Karolina Muchova completed a stunning comeback to upset world number one Ash Barty 1-6 6-3 6-2 in the Australian Open quarter-finals. 

Leading by a set and 2-0 in the second, Barty looked on track to reach back-to-back semi-finals at Melbourne Park, where she was bidding to become the first Australian woman to advance to the final since 1980 and first to lift the trophy since 1978.

But Czech 25th seed Muchova spoiled the 'Barty party' on Rod Laver Arena as her star opponent – unable to stop the rot – sensationally crashed out on Wednesday.

Muchova, whose only previous win against a top-five player came against Karolina Pliskova at Wimbledon two years ago, will contest her maiden major semi-final as either Jennifer Brady or Jessica Pegula await.

Played behind closed doors on the final day of a five-day state-wide lockdown in Victoria, Barty initially showed no mercy in warm and sunny conditions midweek.

Barty, who had lost the second-fewest games (20) en route to the last eight, raced out to a 5-0 lead in just 16 minutes – Muchova managing to avoid a first-set bagel in the only positive in an otherwise forgettable start.

Winner of the 2019 French Open, Barty only dropped three points on first serve, while she won 90 her cent of her second serves – finishing a lopsided first set with six winners and just as many unforced errors.

Progression to the semis appeared to be a foregone conclusion as Barty led and Muchova required a medical timeout away from the court at the end of the third game of the second set.

But Muchova emerged a new player, with Barty fading dramatically after everything she touched had turned to gold in the opening set.

Barty's unforced error count ballooned out to 19 as Muchova enjoyed great success on second serve, winning 12 of 15 points, while the former – who did not face a break point in the first set – only managed four of 15 and served three double faults.

Muchova continued her red-hot form in the deciding set - breaking in the opening game before saving a pair of break points to consolidate and she did not look back as she caused a boilover, which was sealed with an ace.

Data Slam: ​Barty loses her way
Unstoppable in a 24-minute first set, Barty crashed back down to earth thereafter. She missed routine shots consistently, with 31 unforced errors in the remaining two sets contributing to her demise.

WINNERS/UNFORCED ERRORS
Barty – 21/37
Muchova – 17/33

ACES/DOUBLE FAULTS
Barty – 3/3
Muchova – 2/3

BREAK POINTS WON
Barty – 3/13
Muchova – 4/11

Australian Open fans are set to return to Melbourne Park from Thursday after the Victorian government confirmed the lifting of restrictions following a five-day lockdown amid the coronavirus pandemic.

While the number of supporters set to attend remains unknown, fans will be back in their seats for the beginning of the Australian Open semi-finals, with record-chasing Serena Williams set to face three-time grand slam champion Naomi Osaka in Melbourne.

Defending men's champion Novak Djokovic will play the tournament’s surprise package, Russian qualifier Aslan Karatsev - who is the first player to reach a semi-final on their grand slam debut.

Djokovic was on court when the lockdown came into effect last Friday, with the five-day "circuit-breaker" designed to control an outbreak of the UK coronavirus strain.

Part of the third round, the fourth round and quarter-finals of singles action were played behind closed doors after a series of outbreaks in Victoria.

The state has recorded 12 more active cases since the lockdown was implemented but, with none discovered in the past 24 hours, Victorian premier Daniel Andrews announced restrictions will be eased.

"I'm very, very pleased to announce that the restrictions will come off, almost all of them, at midnight tonight," Andrews told reporters on Wednesday.

"From 11:59pm [Wednesday local time], the restrictions will be dropped [but] masks will be required indoors and outdoors when you can't socially distance."

The stage-four restrictions meant residents could not leave their homes for any other reason than work, shopping for groceries, exercise or the giving or receiving of medial care.

This year's delayed Australian Open has had crowds capped at 30,000 per day with original COVID-19 restrictions, but new limits are yet to be determined for the rest of the tournament.

"There will be meetings this afternoon [to determine] what is a safe number," Andrews said.

"They already were reduced, they may have to be reduced further, but that matter will be resolved in the next few hours."

Novak Djokovic lost his temper but refused to let the prospect of Australian Open glory slip away as he edged out Alexander Zverev to reach the semi-finals.

The world number one destroyed a racket when trailing 3-1 in the third set, after he and Zverev split the opening two sets, and it was one of a number of moments when the Serbian showed heightened volatility during a 6-7 (6-8) 6-2 6-4 7-6 (8-6) win.

Still bothered by an abdominal problem that he sustained in the third round, Djokovic nevertheless strides on and will face Russian qualifier Aslan Karatsev for a place in the final.

Zverev, who played in a bright yellow headband and vest top, with a gold medallion hanging from his neck, will look back on an opportunity missed.

As well as that third-set lead, Zverev was also up a break at the start of the fourth, but the US Open runner-up lacked the composure to convert those hard-earned positions.

If Djokovic's racket-smashing was a tactical move designed to gee himself up and distract Zverev, then it worked a treat.

A nip-and-tuck opener had gone the way of German world number seven Zverev, who then made a wretched start to the second set and was 4-0 behind in the blink of an eye.

Just as momentum began to swing back Zverev's way in the third, Djokovic went into his rage, with a ball girl summoned to clear up the mess the 33-year-old created.

Back came Djokovic as double faults began to leak from Zverev's racket, and soon they were into a fourth set.

Zverev led 3-0 but Djokovic was not going away, seizing on mistakes from an opponent who by the end of the second tie-break of the match could only wonder what might have been.

An ace from Djokovic finished off the contest. After eight titles at Melbourne Park, a hunger for more continues to define his every performance in Australia.

"Emotionally I feel a little bit drained. We pushed each other to the limit," Djokovic said in his on-court interview.

"Other than in the second set I started pretty poorly in all the other three sets. I lost my service very early in the first, third and fourth and allowed him to swing through the ball a bit more, but I regained my focus.

"I broke that racket and things started to shift a little bit for me in a positive direction."

Aslan Karatsev said finding stability off the court has helped him become the revelation of this year's Australian Open after the qualifier marched on to the semi-finals.

The Russian became the first qualifier to reach the last four of a major since Vladimir Voltchkov, famously in borrowed shorts, did so in 2000 at Wimbledon.

It was Pete Sampras who eventually blew away Voltchkov's threat at the All England Club on his way to another title.

And it turns out there is a connection between Karatsev and Voltchkov, with both men now calling Minsk their home.

But whereas Voltchkov is Minsk born and bred, Karatsev has taken a roundabout route to setting down roots in the capital of Belarus.

He explained on Tuesday how he was born in the Russian city of Vladikavkaz before moving as a toddler to Israel with his family and living there until the age of 12, when he and his father returned to Russia, spending time in the city of Taganrog.

Tennis took him to training bases in Moscow, then Halle in Germany, Barcelona, and finally Minsk.

It is in Minsk that Karatsev has linked up with former ATP professional Yahor Yatsyk, a man only one year his senior but already settling into coaching.

As Grigor Dimitrov succumbed to injury and slid to a four-set defeat against Karatsev on Tuesday, the unlikely figure in the final four reflected on his long road to this point.

"Yes, I was moving I would say too much," Karatsev said of his nomadic existence.

"In the end I found a coach, Yahor Yatsyk, and this is the right guy for me. He's helped me a lot, more the mental part, and then of course there is the technical stuff as well.

"I like to work with him. We're living in Minsk. We're practicing there."

Karatsev is the lowest-ranked man to reach a grand slam semi-final since Goran Ivanisevic, who won Wimbledon in 2001 on a wildcard entry while ranked 125th in the world.

His charge through the draw makes him only the second qualifier to advance to the Australian Open last four, after Bob Giltinan in December 1977.

"Of course it's amazing that I passed to the semi-finals from qualifying," Karatsev said. "I'm just trying to enjoy the moment and not thinking about that too much and playing from round to round."

He and Yatsyk set the goal of reaching the top 100, which Karatsev had not managed before getting to Melbourne.

Before this fortnight he stood at 114th in the rankings, but he will hurtle to a double-digit ranking next week.

"I think the key is to find the right team, the right coach that I found. I was really lucky to find him," Karatsev said.

"We just met in one tournament. We were saying, 'Okay, let's try to work together', and it's really a big luck that we started to work together and I have a good team around me."

Before he encountered Yatsyk, who as a player did not crack the top 1,000 in singles, Karatsev had a brief moment when he wondered if he might not make the grade.

"There was a time when I was injured that was a difficult time for me because I recovered after the injury, and then 2017 started, and I started to play again, and again I felt the knee," Karatsev said. "I said, 'Whoa.' I quit again for two and a half months, almost three, and I think this is the most difficult part."

Serena Williams is in the Australian Open semi-finals for the first time since she last won a grand slam title, beating Simona Halep to set up a mouthwatering clash with Naomi Osaka.

The American great gained revenge for her Wimbledon final defeat to the Romanian two seasons ago as she conjured a 6-3 6-3 win on Rod Laver Arena.

Halep dropped just four games in that stunning grass-court success in 2019, the third of four grand slam finals that Williams has lost since landing her 23rd major in Australia four years ago.

The 24th title has remained frustratingly elusive, with Williams one away from matching Margaret Court's record haul, but perhaps this is the week where that changes.

She must get past Osaka, her heir apparent as the figurehead for the women's game, but Williams showed her prowess in this match, devastatingly proving a point.

Her power won out, with 24 winners to just nine from Halep, although the 33 unforced errors from Williams showed there is room for improvement in precision.

The tone was set from the first point, Williams with a brilliant forehand service return winner on the forehand side on her way to an immediate break of serve.

Halep forced her way level but Williams raised the tempo in the sixth game and a deep forehand into the Romanian's backhand corner secured a 4-2 advantage.

Williams served out the set to love at the first opportunity but then dipped early in the second set, Halep pinching a break when the American volleyed waywardly at the net.

What proved a consistent theme was Halep's struggle to hit through her opponent, and the two-time grand slam winner could not capitalise on a 3-1 lead in that second set, dropping five successive games as the 39-year-old Williams began to turn on some vintage form.

Dismissive of the often weak Halep serve, Williams swept through to the clash with Osaka.

"I definitely think this was the best match I've played this tournament for sure," Williams said. "I had to, going up against the number two in the world. I knew I had to do better and that's what I did, so I'm excited."

Looking forward to facing Osaka, Williams said in her on-court interview: "She's such a strong player on the court and such an inspirational person off the court, which I think is really cool. I've been watching her and I'm sure she's been watching me."

Former world number one and two-time grand slam champion Yevgeny Kafelnikov believes it is "inevitable" that a Russian player will claim major success as the country's male trio flourish at the Australian Open.

For the first time in the Open Era, three Russian men advanced to the quarter-finals of a slam thanks to star Daniil Medvedev, Andrey Rublev and qualifier Aslan Karatsev in Melbourne.

World number four Medvedev – the 2019 US Open runner-up – will face countryman Rublev in the Melbourne Park quarters as Karatsev meets Grigor Dimitrov for a spot in the semi-finals.

Not since Marat Safin at the 2005 Australian Open has a Russian male won a slam, but Kafelnikov is excited about the future.

"We all know that it's inevitable that they're going to win a slam," Kafelnikov, who was the first Russian man to earn a grand slam singles championship via the 1996 French Open before reigning supreme at Wimbledon three years later, told ATPTour.com.

"It's a question of when and where."

Kafelnikov added: "It was really expected that two of them got to where they are. The third one is a big surprise, but a very happy surprise. I'm very happy for Aslan, finally getting his breakthrough.

"He's going to play a lot of tournaments now without any pressure for the remainder of the 2021 season in terms of getting into the main draws and a big pay cheque will also be a huge boost for him. I'm really happy for him."

Kafelnikov, who won 26 singles titles, continued: "To be honest, I would be happy if one of those guys or even both of them surpass me in terms of number of titles and weeks at number one in the world.

"I'd be happy. I'm not going to be jealous about it. My career was very successful, and hopefully they will have even better [careers]."

Jessica Pegula said she "can't be more confident" after upsetting Elina Svitolina to reach her first grand slam quarter-final and Ash Barty stayed in the hunt for Australian Open glory on Monday.

Pegula, the daughter of NFL and NHL franchise owners of the Buffalo Bills and the Sabres, beat fifth seed Svitolina 6-3 3-6 6-3 on Rod Laver Arena to set up a showdown with her fellow American and friend Jennifer Brady.

Brady made it all the way to the semi-finals of the US Open last year and has now put together her best run at Melbourne Park after seeing off Donna Vekic 6-1 7-5.

World number one Barty has not dropped a set in her home major and started the second week by dispatching Shelby Rogers 6-3 6-4.

The top seed from Queensland's next assignment will be a meeting with Karolina Muchova, who saw the back of Elise Mertens 7-6 (7-5) 7-5.

Muchova, the 25th seed from the Czech Republic, has made it through to her second grand slam quarter-final - having also reached this stage at Wimbledon in 2019 - without losing a set.

Pegula to put friendship to one side

Pegula and Brady are close friends, but they will have to put that to one side when they meet in the quarter-finals.

The world number 61 claimed her first victory over an opponent ranked in the top 10 just over a month after Svitolina beat her in straight sets in Abu Dhabi.

Pegula hit 31 winners to Svitolina's 19 and won 21 points from 29 when she made a trip to the net as she broke new ground at a major

She said: "I can't get more confident, it's my best result yet and I'm playing good tennis. Today was a hard-fought win, so, yeah, feeling pretty good."

Pegula added on the prospect of facing Brady: "We're here to have fun and compete. If I can do it against somebody that I like, that I wouldn't mind if they beat me, hopefully not, but if they did, why not?"

Brady benefited from strict lockdown

Many players understandably struggled during and after being in a strict two-week lockdown in a hotel room following their arrival in Australia.

Brady was among the players who were not allowed out of their rooms for a fortnight, but said she used the situation to recharge her batteries before the first major of the year.

The 22nd-seeded Pennsylvanian said: "I think it was a little bit of a benefit for me, just taking a break from tennis. I had been going non-stop since World Team Tennis in June. I didn't take any time off.

"I was playing from June and then played US Open, the U.S. tournaments, and then went straight to Europe, then finished there and was training in Europe, then went home for Christmas and then came and started in Abu Dhabi.

"So obviously I didn't really feel super fresh mentally coming into Abu Dhabi. And then when I was away from tennis for two weeks, I felt like I wanted to play again to compete and I think that helped me."

Much improved Czech

Muchova had not been beyond the second round of the Australian Open before last week but now has a semi-final spot in her sights.

The 24-year-old was 4-0 down in the opening set as Mertens got off to a flyer but warmed to the task with her battling spirit and positive approach.

Muchova converted five of the six break points she earned on Margaret Court Arena, also coming from a mini-break down in a first-set tie-break.

She struck 25 winners to Mertens' 15 and advanced despite making 31 unforced errors, getting her rewards for throwing caution to the wind.

Rafael Nadal's bid to win a record 21st grand slam title remains on track, while there is a distinctly Russian flavour to the quarter-final line-up at the Australian Open.

World number two Nadal eased past Italian 16th seed Fabio Fognini behind closed doors at Melbourne Park in sunny and warm conditions on Monday.

Daniil Medvedev and Andrey Rublev ensured Russia made history en route to the quarters in Melbourne.

FAMILIAR TERRITORY FOR NADAL

Nadal reached the Australian Open quarter-finals for the 13th time in his career after outclassing Fognini 6-3 6-4 6-2 on Rod Laver Arena.

Stuck on 20 slam championships alongside Roger Federer, who is absent in Melbourne, Nadal is also looking to become the first man in the Open Era to win each of the four majors twice.

The 2009 Australian Open champion was too good for Fognini as Nadal continued his fine run of not dropping a set en route to the last eight in 2021.

Only at the French Open, where he is a 13-time champion, has Nadal reached the quarter-finals more often (14) than at the Australian Open. Federer (15) and John Newcombe (14) are the only men to have reached more Australian Open quarter-finals.

Nadal, who hit 24 winners against Fognini, will face fifth seed Stefanos Tsitsipas for a place in the semi-final after ninth seed Matteo Berrettini withdrew with an abdominal strain before Monday's showdown.

HISTORY FOR RUSSIA​

For the first time in the Open Era, three Russian men have advanced to the quarter-finals of a slam.

Medvedev – the fourth seed – and Rublev joined countryman Aslan Karatsev in the last eight following their respective triumphs on Monday.

Runner-up at the 2019 US Open, Medvedev made light work of American Mackenzie McDonald 6-4 6-2 6-3, extending his winning streak to 18 matches as he reached his maiden Australian Open quarter-final.

"It's an exciting moment to be in the quarters in Australia for the first time. That's a great achievement for me," Medvedev said.

"I want more all the time, but step by step. So this is amazing … I finished at 1.30 [hours], which is important in the later stages of the grand slams, to make fast matches."

It will be an all-Russian affair in the quarters after seventh seed Rublev benefited from a walkover.

Rublev was leading 6-2 7-6 (7-3) when Norway's Casper Ruud retired on Margaret Court Arena.

"At least one of us will be in the semi-finals. So it's good news but yeah, it's going to be a tough match," said Rublev, who featured in last year's French Open quarter-finals.

"Last time he beat me in the quarters in the US Open. So now we're in the quarters in the Australian Open, so we'll see what's going to happen."

Serena Williams is moving better than she has in years, according to her coach Patrick Mouratoglou.

Williams, 39, has looked in good form at the Australian Open as she eyes a record-equalling 24th grand slam singles title.

The American has dropped just one set on her way to the quarter-finals, in which she faces Simona Halep on Tuesday.

Mouratoglou said Williams' movement was the best it has been in several years.

"First of all, it's something that we have put the emphasis on because in tennis that's probably one of the most important things. If you are late on the ball, you can't do what you want to do. Sometimes you don't even touch the ball," he told a news conference on Monday.

"It's a sport where you have to be able to move fast from side to side and long enough. It's something that probably in the last two, three years, this had consequences for Serena.

"Even more, when you're not in a good day, you need a plan B. To be able to have a plan B, you have to be able to move well. If you can't move well, there is no plan B. The only plan is attack.

"I think it cost her a few important matches. So we have decided to find a way to bring back the footwork that she used to have in the past. I feel like she's done a great job. She's moving much better."

Williams last won a major title in Melbourne in 2017, losing four grand slam finals since then.

With all eyes on her as she aims to equal Margaret Court's record of 24 grand slam singles titles, Mouratoglou insisted that mark was not an obsession for Williams.

"Does she need that validation? I don't think she needs that validation.  But, I mean, clearly she came back to tennis to win some other grand slams, so that's for sure the goal," he said.

"Now, she's not as obsessed with the 24 than most of the people in the tennis world, but definitely she wants to win grand slams. That's the only reason why she came back to tennis."

Novak Djokovic fought into the quarter-finals of the Australian Open despite concerns over a muscle injury, seeing off Milos Raonic in four sets.

Djokovic's hopes of defending his title appeared to be in doubt when he said he had a "muscle tear" and was unsure whether he would play the fourth-round clash.

But his history of dominance over Raonic was perhaps a motivating factor in him taking to the court and he stretched his head to head lead to 12-0 with his 300th grand slam win, becoming only the second player in history to reach the landmark.

He did not have it all his own way, a spirited Raonic levelling matters in the second set after losing the first on a tie-break.

However, Djokovic was in control thereafter, progressing 7-6 (7-4) 4-6 6-1 6-4, though a last-eight meeting with Alexander Zverev may prove a sterner test.

Djokovic made it eight wins in nine in tie-breaks with Raonic to take the first set and things looked bleak for the Canadian when he received treatment on his foot in the second set.

But that break proved just the tonic for Raonic as he went on to win a set against Djokovic for the first time in four grand slam meetings.

Yet the tide turned emphatically back in Djokovic's favour in the third – the Serbian winning five straight games to move into a 2-1 lead.

His success came through a familiar strategy against a player of Raonic's power on serve.

Djokovic wasted few opportunities to punish the second serve and consistently took Raonic out of his comfort zone by forcing him into long rallies.

Raonic, to his credit, did save four break points in the fourth set but the dam finally burst and he could not prevent Djokovic from snatching the fifth chance that came his way, the world number one ensuring there was to be no shock as he reached another milestone in a remarkable career.

Data Slam: Djokovic's delightful dozen

Djokovic is through to a 12th quarter-final in Melbourne, the eight-time winner last failing to reach the stage in 2018, when he lost to Hyeon Chung.

WINNERS/UNFORCED ERRORS
Djokovic – 41/25
Raonic – 50/35

ACES/DOUBLE FAULTS
Djokovic – 10/3
Raonic – 26/3

BREAK POINTS WON
Djokovic – 3/11
Raonic – 1/3

Simona Halep set up a quarter-final duel with Serena Williams after showing admirable character to battle back from a set down to beat Iga Swiatek 3-6 6-1 6-4 and seal her 100th grand slam match win.

Halep and Swiatek put on a thrilling show in the night session on Sunday, as the Romanian two-time grand slam champion demonstrated her fighting spirit to come from a set down and reach the last eight.

Swiatek took charge in the first set after saving the first two break points of the contest, eventually putting herself in a commanding position as she won the 10 of the final 11 points of the set, but Halep remained focused as her 19-year-old opponent began to wobble in the second.

Halep then snuffed out any threat of a turnaround by breaking back straight after losing on her own service in the decider and she went on to set up a meeting with Williams, who had overpowered Aryna Sabalenka earlier in the day.

Naomi Osaka also advanced, though she was by no means comfortable, while Hsieh Su-wei beat Marketa Vondrousova in straight sets.

HALEP'S REVENGE

Halep's clash with Swiatek was their first since the French Open last October, when Swiatek ran out a 6-1 6-2 winner and went on to claim her maiden major title.

Revenge was on the cards at Melbourne Park and Halep got the job done impressively, showing her mettle to return from a set down.

"Well, I thought before the match that I have to be a little bit more aggressive than Paris. In Paris I have been very far back, and my ball didn't go through the court," the second seed said. "So, I thought that it's a better chance to go and hit.

"The pressure came from the way I played the last match against her. I just expected a better game from myself, which I did, and I'm really happy about that."

Halep accepts facing Williams will be an entirely different challenge, but she remains confident despite lauding the American a "legend" in her on-court interview.

"Of course it's different, she's the only one with 23 grand slams, so you cannot compare Serena with all of us, because we do not have so many grand slams," Halep added.

"But when I step on the court, it's just another opponent, and always I'm focused on myself more than I focus on who I play. We played so many times. I know what to expect. I will just try to do my game, and I will be confident."

WILLIAMS ON COURSE

All eyes are on Williams yet again, as she hopes to equal Margaret Court's record of 24 grand slam titles – and on the evidence of her latest win, she will take some stopping as she won 6-4 2-6 6-4.

Williams revealed she had to cope with a little off-court stress this week with her clothing line, and Sabalenka certainly kept the pressure up as the 22-year-old took the second set.

But Williams responded well to the seventh seed, who became the first player to take a set off the former world number one. Williams said she remained confident despite that setback.

"Like I said on the court, I just felt like even games that I lost, I was so close to winning. Not all games, but probably most of those games," she said. "I just needed to play better on the big points.  I knew that I could. I still hadn't reached my peak. I was like, 'Okay, Serena, you got this, just keep going.'"

OSAKA RELEASES HER ANGER

Osaka was in a real spot of bother against Garbine Muguruza, but saved two match points.

The 2019 champion Osaka steadied herself and felt more composed after a brief show of frustration, as she struck the ground with her racquet.

Ultimately, she emerged a 4-6 6-4 7-5 victor, and Osaka felt letting frustration get the better of her for a moment helped her cause.

"On the first match point, I was just thinking that I didn't hit a decent serve that entire game, so I should really focus on my serve," he said. "I feel like my serve stats were pretty good that set, so I was just telling myself to do better.

"Then on the second point, when the rally started, I just told myself not to push [the ball] but also don't do something crazy and make a really bad unforced error. I felt the entire match I was overthinking. There was a moment when I got angry and hit my racquet on the ground. I feel like I released a lot of the thoughts that I had. It just made me go more into instinct-based tennis."

She will face Hsieh next, the world number 71 having beaten Vondrousova – ranked 51 places higher – 6-4 6-2.

Serena Williams calmed injured fears after coming through a thrilling back-and-forth against Arnya Sabalenka to reach the quarter-finals of the Australian Open.

Williams, who is pursuing a record-equalling 24th career grand slam and her first major victory in four years, prevailed 6-4 2-6 6-4 after more than two hours on court against seventh seed Sabalenka.

Her struggles during the second set appeared partly attributable to a fall but Williams recovered her poise and the 39-year-old does not expect any ill-effects in a last-eight showdown against either Simona Halep or Iga Swiatek.

"I don't think so. It didn't hurt at all. I didn't roll my ankle, so that was good," she told reporters.

"Yeah, I think it was just dramatic, me being dramatic.

"My first thought was, 'Not another ankle sprain in Australia'. But I knew immediately that it wasn't.

"Then I was more embarrassed than anything. I was like, 'Oh, my goodness'."

Williams moved well throughout the contest, assuaging any lingering concerns over Achilles problems that have dogged her of late - even manging to rally when Sabalenka reeled off three consecutive games from 1-4 down in the decider.

"I've worked really hard on my movement. Yeah, I like retrieving balls. I mean, obviously I like to be on the offense, but I can play defence really well, as well.

"I do get a lot of balls back when I need to. I didn't think about my Achilles. It's so good to not think about it. Oh, my goodness. It's been a problem actually since 2018.

"I just never want that problem again. It feels really good to just play and to run, to not feel that. It's a great relief."

Arguably Williams' greatest inconvenience around the match was not a physical one, after she had to participate in a Saturday conference call to avert an "emergency" at her clothing business.

"Tennis is a lot less stressful. I don't have to manage a team. I do manage a team actually, but it's different," she chuckled. "Even though I am the CEO of my tennis team, it's definitely different.

"I think a part of me loves being on the court because it's free-flowing. It's not like I have to kind of just manage and make sure everyone is able to perform.

"I have a second career and it's fun. One of our main players, our employees, had an emergency. You got to step it up when you got to step it up.

"I was smart about that. I scheduled a call directly after my practice. I was like, 'Okay, I can do it early and still have the rest of the day to relax'.

"And it was during [Williams' daughter] Olympia's nap, so it was perfect."

Dominic Thiem's bid to reach back-to-back Australian Open finals was dashed by Grigor Dimitrov as the US Open champion surprisingly crashed out in the round of 16.

Thiem lost a thrilling final to Novak Djokovic in last year's Melbourne Park decider before breaking through for his maiden grand slam title at Flushing Meadows later in 2020.

But Thiem failed to secure another second-week berth in Melbourne, where the third seed was stunned 6-4 6-4 6-0 by former world number three Dimitrov on Sunday.

Thiem was aiming to reach the Australian Open quarter-finals for the second time and become the second Austrian man to feature in the quarters in Melbourne on multiple occasions after Thomas Muster (1989, 1994 and 1997).

The 27-year-old Thiem was also bidding to reach his ninth slam quarter-final and equal Muster's record for most major last-eight appearances by any Austrian – male or female.

However, Thiem – who rallied from two-sets-to-love down to top Nick Kyrgios in the previous round – was no match for Dimitrov behind closed doors on Rod Laver Arena amid a coronavirus lockdown in Victoria.

Both players hit 25 winners, but Dimitrov only tallied 18 unforced errors to Thiem's 41 following just over two hours on court.

Dimitrov progressed to his fourth Australian Open quarter-final, extending his record for most last-eight appearances at Melbourne Park by a Bulgarian player – man or woman.

An Australian Open semi-finalist in 2017, Dimitrov will now contest his sixth grand slam quarter-final – the 29-year-old is third for most quarter-final appearances by a Bulgarian player, behind Manuela Maleeva (nine) and Katerina Maleeva (seven).

Rafael Nadal was able to offer a positive update on his fitness after easing into the second week at the Australian Open.

The 20-time grand slam champion is playing in his first tournament since November's ATP Finals and faced a battle to make the Melbourne major due to a back problem.

But Nadal has made the fourth round without dropping a set, seeing off Cameron Norrie 7-5 6-2 7-5 on Saturday.

"I did things well, [then there are] things that I need to improve. Something normal," the Spaniard said. "But, yes, happy, of course. Second week, straight sets. Can't complain."
 

PAIN RELIEF AT LAST FOR RAFA

Nadal might have been similarly dominant in his prior matches but revealed after beating Norrie he is only now feeling fitter.

"No, the back was not getting better each day; it was getting better today," he said. "But today is better, yeah, the first day I feel an improvement, and that's the most important thing for me today, more than any other thing.

"Of course, I was not serving my normal serve for the last 15 days. Today is the first day that I started to serve again my normal serve.

"But yesterday I didn't practice, so today was just warming up with the new, normal movement.

"So, of course, I didn't serve bad, but I can do better, I think. And I'm looking forward to doing it better. It has been an important victory for me.

"The biggest victory is the back is better for the first day. That's the most important thing."

Nadal will face Fabio Fognini next after he ended Australia's interest in the home grand slam with a 6-4 6-3 6-4 victory over Alex De Minaur, the host nation's final hope.

"It's one of those matches," an impressed De Minaur said. "You're out there leaving it all out there, but you can just feel that he's playing at another level."
 

MOODY MEDVEDEV MAKES AMENDS

There are three Russian men in the last 16 for the first time in Melbourne in the Open Era, but the country's biggest name survived a major scare.

Daniil Medvedev was cruising after taking the first two sets against Filip Krajinovic, only to drop the next two and engage in an angry back-and-forth with coach Gilles Cervara.

Cervara eventually left Medvedev's box as the fourth seed trailed 4-1 in the fourth set and did not return, but the 25-year-old recovered to get the job done in dominant fashion, a 6-3 6-3 4-6 3-6 6-0 victor.

Medvedev, with Mackenzie McDonald next, said of the incident with Cervara: "He said just before leaving that he's sure I'm going to win the match, but he's going to leave to let me be more calm.

"Sometimes maybe I will disagree but this time for sure it was a good thing to do.

"Today it helped, and definitely we're going to talk about it a little bit, but there is not a big deal."

Andrey Rublev joined Medvedev and compatriot Aslan Karatsev in the fourth round as he improved to 7-0 for the year with a three-set defeat of Feliciano Lopez. He will play Casper Ruud.
 

HISTORY CHANNEL OVER CHAMP

Defending champion Novak Djokovic's struggles with injury on Friday might have intrigued much of the tennis public, but Stefanos Tsitsipas was not overly concerned.

The fifth seed, who breezed past Mikael Ymer, did not watch the match and revealed he has little interest in keeping up with the exploits of his rivals.

"I might watch [Djokovic and Nadal] a little bit on TV if it happens that the TV is on or the right channel is on," he said. "Otherwise I just switch to History Channel.

"Definitely not tennis history. I think I have enough of tennis being in here every single day."

Tsitsipas will next play Matteo Berrettini, who is enjoying his best run at the Australian Open and saw off a side complaint to advance in three sets by edging Karen Khachanov, another Russian, in a trio of tie-breakers.

Ash Barty may have her focus on winning the Australian Open right now but suggested a career change could be on the cards in the future.  

The world number one made sure she will still be competing during the second week of the tournament in Melbourne by beating Ekaterina Alexandrova in straight sets.  

But, having played international cricket for Australia before switching to tennis, could the multi-talented Barty be considering trying another sport?  

Elsewhere in Saturday's action, Karolina Pliskova lost her cool – and also a couple of rackets – as she slipped to defeat against the impressive Karolina Muchova in an empty Rod Laver Arena, with fans not able to be present due to a five-day lockdown in the state of Victoria.

Elina Svitolina had no such problems in her third-round match, while Elise Mertens was victorious in just over an hour against Belinda Bencic. Jennifer Brady ended Slovenian qualifier Kaja Juvan's run in the first grand slam of the year.

AUSSIE RULES, OK? 

After winning 6-2 6-4 without ever needing to be at her peak, Barty was cheekily asked by former doubles partner Casey Dellacqua – now working in the media – whether she may be set to switch paths again, once her tennis career has come to an end.  

Australian rules football was the answer – but Dellacqua maybe got more than she bargained for from her former playing partner during the on-court interview. 

"I thought it was our deal, we're going to AFLW. It's ABCD [the nickname for the pairing from their doubles career]. We come as a package, and I know we will be going to the [Richmond] Tigers that is for sure," Barty said. "You can't go to Carlton. You have to come to the 'Tiges' with me."

Dellacqua replied: "I need to get out there and start practicing some kicking, but you are good. I would love to do that one day." 

For Barty, though, the next challenge facing her is Shelby Rogers, who knocked out 21st seed Anett Kontaveit during the evening session.  

MAKING A RACKET 

A disgruntled Pliskova was not impressed when punished for smashing up a racket during her match with compatriot Muchova. 

Having received a warning when throwing a racket to the floor during the course of the final game in the opening set, the sixth seed then vented her frustration again on another while in the players' tunnel.  

An official witnessed the incident and reported it to chair umpire Alison Hughes, who punished the Czech with a point penalty before she began serving to open the second set.  

"It's off court, I'm allowed to do what I want," Pliskova insisted when querying the decision to the official. She would go on to hold before recording two successive breaks, yet somehow failed to force a decider.  

Muchova rallied from 5-0 down in sensational fashion, winning seven games on the spin to triumph 7-5 7-5 to make it through to the last 16.

CONTRASTING PROGRESS FOR SEEDS

Svitolina has still yet to drop a set in the tournament after overcoming 26th seed Yulia Putintseva by a 6-4 6-0 scoreline.  

The fifth seed was twice down a break in the first set but, after eventually coming out on top to take a 1-0 lead, breezed through the second in a hurry.  

"She has a very different game style from what I played my last two rounds, so it wasn't easy at the beginning to adjust," Svitolina said. "As soon as I was feeling better, I just stepped my game, and it was quite a comfortable win after." 

Next up will be Jessica Pegula, who is through to the fourth round at a slam for the first time in her career after thrashing Kristina Mladenovic 6-2 6-1.  

There was also success for another American in the main draw, Brady defeating Juvan in straight sets. Her reward is a clash with Donna Vekic, the 28th seed having to save a match point before eventually seeing off Kaia Kanepi 5-7 7-6 (7-2) 6-4 after two hours and 38 minutes on court.