Ash Barty will meet Aryna Sabalenka in the Stuttgart Open final after Simona Halep's quest to win the tournament for the first time fell short.

World number three Halep had claimed straight-set wins over Ekaterina Alexandrova and Marketa Vondrousova en route to the semi-finals, but met her match in the form of Belarusian Sabalenka, who triumphed 6-3 6-2.

A nine-time singles champion, Sabalenka made it into a 14th career final without conceding a single break, as she managed to keep Romanian Halep at arm's length.

Standing between Sabalenka and a 10th singles title is world number one Barty who, on her 25th birthday, came from behind to defeat Elina Svitolina 4-6 7-6 (7-5) 6-2.

Making her tournament debut in Stuttgart, Barty had overcome Laura Siegemund and Karolina Pliskova, but found herself at 5-4 down in the second set, with Svitolina serving for the match.

The fourth seed failed to take her chance, with Barty breaking and subsequently biting back in the tie-break, before carrying the momentum into the decider to claim a third straight win over Svitolina.

Top seed Elise Mertens made it to her second Istanbul Open as she saw off her doubles partner and birthday girl Veronika Kudermetova 6-1 6-4.

It means Mertens will be playing in two finals on Sunday, as she pairs up with Kudermetova again in the doubles showdown against Nao Hibino and Makoto Ninomiya.

Mertens' win ended Charleston champion Kudermetova's nine-match winning streak, and set up a final against the unseeded Sorana Cirstea, who defeated Marta Kostyuk 6-4 6-4.

World number one Ash Barty survived a scare to reach the semi-finals of the Stuttgart Open with a 2-6 6-1 7-5 win over Karolina Pliskova.

The Australian started slowly in the quarter-final of the WTA 500 tournament on Friday as Pliskova broke her serve twice in taking the first set, before Barty hit back with three breaks of her own to force a decider.

Barty was two points away from losing on five occasions as world number nine Pliskova served for the match at 5-4 in the final set.

But she broke the Czech's resolve eventually, sealing victory when Pliskova hit the ball long after a baseline rally.

The win was Barty's eighth consecutive victory over a top-10 opponent and she said in a media conference afterwards that facing top players in the world brings the best out of her.

"When you come up against top-10 opponents, you have to go to that level above to be able to compete. They force you to bring your best," Barty said.

"With a lot of the girls in the top 10, we've had plenty of matches that have gone either way, different experiences, so each time I love that challenge of testing myself against the best."

Barty will face Elina Svitolina in the semi-finals after she saved two match points to claim a 6-7 (4-7) 7-5 6-2 victory over Petra Kvitova.

In the other half of the draw, Simona Halep breezed through to the semi-finals with a 6-1 6-4 win over Ekaterina Alexandrova.

Halep clinically closed out the first set, and although Alexandrova showed more fight in the second, the world number three did not allow her a route back into the match.

Halep will face Aryna Sabalenka following the Belarusian's 7-5 4-6 6-1 win over Anett Kontaveit.

In the Istanbul Cup, top seed Elise Mertens secured her place in the semi-finals with a 6-4 6-4 win over Katerina Siniakova.

Mertens will face Veronika Kudermetova who fought back from a set down to clinch a 2-6 6-3 6-3 win over Ana Bogdan.

The other semi-final will see Sorana Cirstea play Marta Kostyuk. Cirstea progressed after Fiona Ferro, trailing 6-4, retired through injury while Kostyuk beat Ana Konjuh 7-5 4-6 6-3.

World number one Ash Barty has been knocked out of the Charleston Open after a straight-sets loss to unseeded Spaniard Paula Badosa in Friday's quarter-finals.

Badosa won 6-4 6-3 over the favoured Australian in one hour, 16 minutes to book a spot in the last four on the green clay and a meeting with 15th seed Veronika Kudermetova.

Kudermetova beat 2017 US Open winner Sloane Stephens 6-3 6-4 in her first win over a grand slam winner.

Former French Open junior champion Badosa, who beat fifth seed Belinda Bencic in the second round, claimed her second career victory over a top-20 player against Barty.

Barty may have hit 34 to 19 winners but she also made twice as many unforced errors, 24 to 12.

The Spaniard broke Barty's serve five times while she sent down seven aces and saved 12 of 14 break points.

"I was quite nervous today but I think I served very well and I think that was the key for the match," Badosa said in her on-court interview.

"It was a tough match but I was there until the last moment and I managed to win."

World number 71 Badosa becomes the lowest-ranked player to beat Barty since September 2019.

The Australian had won eight matches in a row after last week's triumph at the Miami Open.

Unseeded Montenegrin Danka Kovinic came from a set down to topple 11th seed Yulia Putintseva 6-7 (2-7) 7-5 6-1.

Kovinic, who knocked out Petra Kvitova in the third round, will play 12th seed Ons Jabeur in the semi-finals after she overcame Coco Gauff 6-3 6-3.

Meanwhile, at the Copa Colsanitas in Bogota, fifth Tamara Zidansek beat Italy's Sara Errani 6-3 6-4 to claim a spot in the semi-finals.

Viktoriya Tomova outlasted qualifier Nuria Parrizas-Diaz 5-7 6-2 6-4 in almost two and a half hours, while Harmony Tan and local wildcard Maria Camila Osorio Serrano also won.

Top seed Ashleigh Barty moved into the quarter-finals with a three-set win over Shelby Rogers while Petra Kvitova and Garbine Muguruza exited in the Round of 16 of the Volvo Car Open in Charleston.

World number one Barty was pushed all the way by 52nd ranked Rogers, with both players trading breaks in the final set, before the Australian prevailed 7-6 (7-3) 4-6 6-4.

The victory extends Barty's winning streak to eight matches having won last week's Miami Open.

Barty won 82 per cent of first serve points and sent down 10 aces to get the edge on the American, who saved eight of 13 break points throughout the match.

"The conditions are difficult. It's pretty quick," Barty said in her on-court interview post-game.

"Shelby was able to control the centre of court for a lot of the match. It was about trying to get control when I could. She's an exceptional player, it's always a fight no matter what surface or where we are in the world. It's always one that I enjoy."

Barty will play Spaniard 71st ranked Paula Badosa in the quarter-finals after she beat Caty McNally 6-3 6-3.

Third seed Kvitova was the major casualty on Thursday, losing 6-4 6-1 to Montenegrin Danka Kovinic.

The first set was tightly fought before Kovinic pulled away as Kvitova's errors mounted.

"We both have pretty big serves and she's very good hitting from the baseline," Kovinic said post-game. "Today it was the key that I tried, and did it really well, to take her pace of the ball and use her energy."

Sixth seed Garbine Muguruza also bowed out injured, despite leading 6-0 2-2 against 11th seed Yulia Putintseva.

Muguruza laboured for a few games after a medical time-out before retiring with a left leg injury. Putintseva will next face Kovinic.

Seeds Ons Jabeur, Veronika Kudermetova and Cori Gauff also progressed to the last eight, while Sloane Stephens won in straight sets against Ajla Tomljanovic.

Meanwhile at the Copa Colsanitas second round in Bogota, seventh seed Tereza Martincova was knocked out, going down 6-3 6-3 to Colombian teenager Maria Osorio Serrano.

On the outdoor clay courts, fifth Tamara Zidansek moved into the quarter-finals with a 6-2 6-3 win over Giulia Gatto-Monticone, while Harmony Tan beat Daniela Seguel.

Ash Barty won her first match on clay since reigning supreme at the 2019 French Open as the world number one rolled into the Volvo Car Open round of 16.

Barty – who last featured in a clay-court match en route to Roland Garros glory almost two years ago amid the coronavirus pandemic – made light work of Misaki Doi 6-2 6-1.

Miami Open champion last week, top seed Barty continued where she left off at the WTA 500 event on Wednesday, closing out proceedings in just over an hour in Charleston.

"I had to use it as an opportunity to try and build some comfort," Barty said. "I think having a couple days between Miami and playing this first match was important, to have my body rest, but to also try and prepare to change surfaces. It was a very quick turnaround, but I felt great out there tonight."

Barty – who now boasts a 15-2 win-loss record in 2021 – will next face Shelby Rogers after she outlasted 13th seed Amanda Anisimova 1-6 7-5 6-4.

As for second seed Sofia Kenin, the 2020 Australian Open champion slumped to a shock 4-6 6-3 6-4 defeat against Lauren Davis midweek.

World number four Kenin – runner-up at last year's French Open – eased to the first set but fellow American Davis, ranked 79th in the world, changed tactics to fine effect.

"I was a bit uncomfortable so I just really dug deep and really started to think about how to beat her and I found that heavy deep balls were not her favourite," the 27-year-old Davis said.

"Being on clay, the ball bounces high, pushing girls back, so it's very effective."

Kenin took a medical timeout at 3-0 down in the deciding set but, despite reeling off the next three games, she was unable to see Davis off as her 2021 woes continue.

Davis now heads into another all-American clash with teenage sensation Coco Gauff – who came from 1-3 down in the third to defeat Liudmila Samsonova 4-6 6-1 6-4 in an absorbing two-hour contest.

Belinda Bencic – the fifth seed – crashed out as Paula Badosa claimed the first top-20 win of her career following a 6-2 6-7 (2-7) 6-1 success.

Badosa will face Caty McNally in the last 16 after the 19-year-old American beat Anastasija Sevastova 7-6 (7-3) 2-6 6-4.

Seventh seed Elise Mertens was another big name to depart as Alize Cornet prevailed 7-5 6-3, although 15th seed Veronika Kudermetova and 12th seed Ons Jabeur progressed in with the minimum of fuss.

Former US Open champion Sloane Stephens, meanwhile, topped eighth seed Madison Keys 6-4 6-4.

Seeds were even more vulnerable at the Copa Colsanitas in Bogata, including the top-seeded Saisai Zheng who was dispatched 6-4 6-1 by Stefanie Voegele.

Zheng's compatriot Yafan Wang, seeded eighth, went down 6-3 6-3 to Viktoriya Tomova.

Arantxa Rus and Jasmine Paolini, the third and sixth seeds respectively, lost in three to Spanish duo Nuria Parrizas Diaz and Lara Arruabarrena.

World number one Ashleigh Barty maintained her winning run in Miami with her best performance of the 2021 tournament to date dispatching of Elina Svitolina to book a spot in the final.

Barty defeated fifth seed Svitolina 6-3 6-3 in Thursday's semi-final, hitting 27 winners and breaking her Ukrainian opponent five times.

The Australian had been down a match point in her opening clash of this year's Miami Open against Kristina Kucova but the 2019 champion has responded to every challenge since.

However, Barty needed three sets to overcome both Victoria Azarenka and Aryna Sabalenka in earlier rounds before making more light work of Svitolina to make it 11 straight wins in Miami, given 2020's event was cancelled.

Barty will play 2019 US Open winner Bianca Andreescu in Saturday's final after she defeated Naomi Osaka's conqueror Maria Sakkari 7-6 (9-7) 3-6 7-6 (7-4) in Thursday's other semi-final.

"Yeah, I think it was," Barty said in her on-court interview when asked if it was her best match of the tournament.

"I think [with] Elina, you have to produce your best tennis. Happy with the way we were able to execute today."

Svitolina went into the match with a 5-1 head-to-head advantage over Barty, while the Australian had not played on foreign soil prior to the event since February 2020, opting to step away from the tour during the COVID-19 pandemic.

"With the head-to-head we had, I almost see myself as the underdog, I really do," Barty said.

"It gives me the chance to go out there and play with freedom. To play not careless but carefree tennis."

Barty has reinforced her world number one ranking from Osaka, who lost to Sakkari in the quarters, by progressing this far although adding a second Miami Open title will be top priority.

The 24-year-old 2019 French Open champion had a medical timeout between sets to tend to a preexisting abdominal issue but said she would be fine for the decider on Saturday.

"Yeah, I was a little bit sore," she said. "I got some assistance with some tape on it. But knowing we’ve got a day to recover tomorrow, I promise you I’ll be right as rain and then we’ll be good to go."

Eighth seed Andreescu booked her place in the decider with a strong three-set victory over 23rd seed Sakkari in a match which finished in the early hours of Friday morning.

The Canadian won in two hours and 42 minutes in a match full of momentum shifts, as Andreescu won her fourth three-setter in five matches in Miami this week.

World number one Ashleigh Barty maintained her winning run in Miami with her best performance of the 2021 tournament to date dispatching of Elina Svitolina to book a spot in the final.

Barty defeated fifth seed Svitolina 6-3 6-3 in Thursday's semi-final, hitting 27 winners and breaking her Ukrainian opponent five times.

The Australian had been down a match point in her opening clash of this year's Miami Open against Kristina Kucova but the 2019 champion has responded to every challenge since.

However, Barty needed three sets to overcome both Victoria Azarenka and Aryna Sabalenka in earlier rounds before making more light work of Svitolina to make it 11 straight wins in Miami, given 2020's event was cancelled.

Barty will play 2019 U.S. Open winner Bianca Andreescu in Saturday's final after she defeated Naomi Osaka's conqueror Maria Sakkari 7-6 (9-7) 3-6 7-6 (7-4) in Thursday's other semi-final.

"Yeah, I think it was," Barty said in her on-court interview when asked if it was her best match of the tournament.

"I think [with] Elina, you have to produce your best tennis. Happy with the way we were able to execute today."

Svitolina went into the match with a 5-1 head-to-head advantage over Barty, while the Australian had not played on foreign soil prior to the event since February 2020, opting to step away from the tour during the COVID-19 pandemic.

"With the head-to-head we had, I almost see myself as the underdog, I really do," Barty said.

"It gives me the chance to go out there and play with freedom. To play not careless but carefree tennis."

Barty has reinforced her world number one ranking from Osaka, who lost to Sakkari in the quarters, by progressing this far although adding a second Miami Open title will be top priority.

The 24-year-old 2019 French Open champion had a medical timeout between sets to tend to a preexisting abdominal issue but said she would be fine for the decider on Saturday.

"Yeah, I was a little bit sore," she said. "I got some assistance with some tape on it. But knowing we’ve got a day to recover tomorrow, I promise you I’ll be right as rain and then we’ll be good to go."

Eighth seed Andreescu booked her place in the decider with a strong three-set victory over 23rd seed Sakkari in a match which finished in the early hours of Friday morning.

The Canadian won in two hours and 42 minutes in a match full of momentum shifts, as Andreescu won her fourth three-setter in five matches in Miami this week.

Ash Barty's grip on the world number one ranking remains for now after winning in three sets against seventh seed Aryna Sabalenka in the Miami Open quarter-finals on Tuesday.

The 2019 Miami Open champion defeated Sabalenka 6-4 6-7 (5-7) 6-3 in humid conditions in South Florida to reach the last four, where the Australian will face fifth seed Elina Svitolina.

Svitolina won in the later match on Tuesday over Latvia's Anastasija Sevastova 6-3 6-2.

Barty, the 2019 French Open champion, did not drop her serve once against the Belarusian, saving seven break points throughout the match as she bids to retain her top ranking.

Barty is under threat from 2021 Australian Open winner Naomi Osaka for the number one ranking, with the Japanese also into the quarters.

The Australian will retain the top ranking by reaching the decider, regardless of second seed Osaka's results.

"It was a brilliant match today," Barty said in her on-court interview. "It was certainly the best level I’ve played for a long time and especially over a sustained period.

"Aryna really made me bring out my best stuff today. She’s an exceptional competitor."

Barty has now won 10 consecutive matches in Miami, dating back to her 2019 title with 2020's event cancelled due to the COVID-19 pandemic.

Ukraine's Svitolina, ranked fifth in the world, reached the Miami Open semi-finals for the first time with her win over the unseeded Sevastova.

"I've always wanted to play well here in Miami," said Svitolina, who made last year's French Open quarter-finals.

"It's one of the biggest tournaments and playing here is always amazing, so I'm really pleased with the performance tonight."

World number two Naomi Osaka and defending champion Ash Barty advanced to the quarter-finals of the Miami Open.

Osaka reached the last eight at the WTA Premier event for the first time in her career thanks to Monday's straight-sets win over Elise Mertens.

World number one Barty overcame two-time grand slam champion Victoria Azarenka in a tough three-set battle in Miami.

THERE'S NO STOPPING OSAKA

Australian Open champion Osaka extended her winning streak to a remarkable 23 matches.

Osaka defeated 16th seed Mertens 6-3 6-3 to stay hot – Venus Williams, Serena Williams, Justine Henin and Azarenka are the only other players with winning streaks of 23 or more matches since 2000.

"It definitely feels very special," four-time major winner Osaka said. "This is one of my favourite tournaments to play, and of course I'm sad I hadn't been able to get to the second week the last times that I have played this tournament. But I'm here now, and hopefully it will go well this time."

Maria Sakkari is next for Osaka after the 23rd seed saved six match points in her 6-4 2-6 7-6 (8-6) win over Jessica Pegula.

BARTY WINS BATTLE OF PAST AND PRESENT NUMBER ONES

In a rollercoaster battle, top seed Barty prevailed 6-1 1-6 6-2 against 14th seed Azarenka.

Barty extended her winning streak in Miami to nine matches after coming out on top against the former world number one.

"Playing against Vika you have to be ready right from the first point," Barty said. "I felt like I did that well in the first set and she gave me a few cheap errors. Then through the second she lifted her intensity.

"I probably wasn't sharp enough in those first couple of games to be able to go with her, particularly with new balls. When Vika is ahead and she's a front runner, she's the very best in the world."

Aryna Sabalenka stands in the way of Barty and the semi-finals after the seventh seed trounced Marketa Vondrousova 6-1 6-2.

SVITOLINA WINS THRILLER, ANDREESCU RALLIES

Fifth seed Elina Svitolina rallied past two-time Wimbledon winner Petra Kvitova 2-6 7-5 7-5.

Svitolina made a slow start against the red-hot ninth seed, but the 2018 WTA Finals champion finished strongly to progress.

Anastasija Sevastova took down Ana Konjuh 6-1 7-5 to set up a clash with Svitolina.

Meanwhile, eighth seed and 2019 US Open champion Bianca Andreescu came from behind to defeat two-time slam winner Garbine Muguruza 3-6 6-3 6-2.

World number one Ash Barty moved through to the last 16 of the Miami Open, where Simona Halep's campaign came to a premature end.

Defending champion and top seed Barty was too good for Jelena Ostapenko in Saturday's showdown between the former French Open winners.

Two-time grand slam winner Victoria Azarenka also moved through to the fourth round of the WTA Premier tournament.

Halep, however, succumbed to a shoulder injury in Miami.

CLASH OF PAST AND PRESENT NUMBER ONES

Barty and former world number one Azarenka will go head-to-head for a place in the quarter-finals.

Australian star Barty accounted for Ostapenko 6-3 6-2 as she extended her winning streak at the Miami Open to eight matches.

Barty, who tallied nine winners to 14 unforced errors, rallied from 2-0 down in the second set by reeling off six successive games to advance.

"Today felt like I was a lot sharper and switched on and ready to go from the very first point," Barty said afterwards.

Three-time Miami champion Azarenka trumped Angelique Kerber 7-5 6-2 in the third round.

Azarenka – the 14th seed – fought back from a 4-1 deficit in the opening set to get the better of the three-time major winner.

"She's a very talented player. I always have been a huge fan of her game and the way she plays, the way she handles herself. She has a lot of variety," Azarenka said on facing Barty. "She has pretty much every single shot there is. [It's] going to be a great match."

INJURED HALEP PULLS OUT

Two-time grand slam champion Halep withdrew due to a shoulder injury as Anastasija Sevastova benefited from a walkover.

"I'm very sorry to I have to pull out of the singles and doubles at the Miami Open, but my injury doesn't let me play here as expected," said Halep.

"I'm sad that I can't continue, I wanted to come here to give my best and play many matches but unfortunately I can't. 

"Hopefully next year I will come back healthy and better."

Next up for Sevastova is wildcard Ana Konjuh, who stunned 15th seed and reigning French Open champion Iga Swiatek 6-4 2-6 6-2.

SVITOLINA AND SABALENKA ROLL ON

Ukrainian fifth seed Elina Svitolina booked her spot in the round of 16 after overcoming fellow seed Ekaterina Alexandrova 7-6 (7-1) 6-4.

Two-time Wimbledon winner Petra Kvitova stands in the way of a quarter-final berth – the ninth seed was too good for 17th seed Johanna Konta 6-1 6-2.

Seventh seed Aryna Sabalenka, meanwhile, prevailed 7-6 (7-4) 6-4 against Veronika Kudermetova.

Belinda Bencic – the 11th seed – was sent packing 4-6 6-4 6-4 by Marketa Vondrousova, who will take on Sabalenka.

Ash Barty completed a great escape to stay alive at the Miami Open, where Simona Halep also progressed.

Barty faced a match point but the defending champion and world number one dug deep to prevail in three sets against Kristina Kucova on Thursday.

Romanian third seed Halep also needed three sets at the WTA Premier tournament in Miami.

BARTY PRODUCES COMEBACK

In her first match outside of Australia in more than 12 months, Barty survived to top qualifier Kucova in Miami.

Barty trailed 5-2 in the third set, with Kucova earning a match point at 5-3 but the Australian star saved it and won the final five games of the match to secure a spot in the round of 32.

Winner of the 2019 French Open, Barty sent down an equal career-high 15 aces in two-and-a-half hours.

"Today was really hard work, and I enjoyed every single minute of it," Barty said on court post-game. "There’s nothing like coming through a test like that, and now I get another opportunity in a couple days' time to play another tough match and test myself again."

Next up for Barty is 2017 Roland Garros champion Jelena Ostapenko, who outlasted Kirsten Flipkens 6-2 5-7 6-3.

HALEP REACHES MILESTONE

Halep brought up her 400th WTA main-draw triumph with a 3-6 6-4 6-0 victory over France's Caroline Garcia.

After dropping the opening set, Halep won 11 of the final 12 games to move through to the next round.

Halep won in one hour, 48 minutes, drastically improving on her first serve after the opening set while coming to grips with Garcia's kick serve.

"I needed time to get used to it and to get the rhythm," Halep said about Garcia's serve having improved her head-to-head record to 7-1, with Anastasija Sevastova awaiting in the last 32 after eliminating American sensation Coco Gauff.

Halep received attention on her shoulder early in the second. "I struggled with my serve," Halep said. "I struggled with my shoulder a little bit, so the attention was a little bit on the pain. [After that] I started to relax myself."

KERBER'S DOUBLE BAGEL

Three-time grand slam winner Angelique Kerber has been up and down in recently, but she flexed her muscles with a 6-0 6-0 humiliation of Renata Zarazua.

Aryna Sabalenka – the seventh seed – was another one to fend off match points before rallying 0-6 6-3 7-6 (11-9) past Bulgarian qualifier Tsvetana Pironkova in a gutsy.

Last year's French Open champion Iga Swiatek knocked off Barbora Krejcikova 6-4 6-2, while ninth seed and two-time Wimbledon champion Petra Kvitova got past Aliza Cornet 6-0 6-4.

Fifth seed Elina Svitolina survived to beat Shelby Rogers 3-6 7-5 6-3 and two-time major winner Victoria Azarenka benefited from a walkover.

Sloane Stephens ended her losing run to start the year with a hard-fought three-set win over France's Oceane Dodin in the first round of the Miami Open on Wednesday.

Former US Open champion Stephens, ranked 49th in the world, defeated Dodin 6-7 (6-8) 6-4 6-2.

Stephens progresses to the second round where the top seeds, including top three Ash Barty, Naomi Osaka and Simona Halep, will be introduced and she will face 28th seed Amanda Anisimova.

Danielle Collins, Wang Qiang, Alize Cornet and Caroline Garcia were among the other winners on Wednesday, while Svetlana Kuznetsova bowed out.

SLOANE FIGHTBACK

Stephens had endured a dismal start to 2021, enduring an 0-4 win-loss record to begin the year.

The 28-year-old American was made to do it the hard way against Dodin on Wednesday, dropping the first set in a tie-break.

Stephens improved on her return in the second set, winning 73 per cent of points off Dodin's second serve before running away with the match in the last.

"It's been a rough one for me lately, so I'm really pleased to get through that, fight my way through it and make it happen somehow," Stephens said post-match.

FORMER MAJOR WINNER GONE

Two-time grand slam winner Kuznetsova was the major first-round casualty, going down 2-6 6-2 6-1 to France's Alize Cornet.

Kuznetsova, who is now ranked 35th in the world, bows out with Cornet to face ninth seed Petra Kvitova.

Collins got past France's Kristina Mladenovic 6-3 6-3 with the 40th-ranked American setting up a second-round clash with 32nd seed Veronika Kudermetova.

Wang, ranked 38th in the world, also progressed despite dropping a set in a 6-1 3-6 6-3 win over Spanish qualifier Aliona Bolsova.

SECOND-ROUND MATCH-UPS

The round of 64 will commence on Thursday, with third seed Halep to face Garcia who got past another Romanian, Mihaela Buzarnescu 6-1 6-2.

Top seed Barty will be in action against Slovakia's Kristina Kucova, while fourth seed Sofia Kenin will take on former top-10 player Andrea Petkovic.

Second seed Osaka has an assignment against 77th-ranked Australian Ajla Tomljanovic, while 14th seed Victoria Azarenka is already into the third round with opponent Laura Siegemund withdrawing after her win on Tuesday.

Ash Barty crashed out of the Adelaide International at her first hurdle after going down in straight sets to Danielle Collins.

It took only 65 minutes for American Collins to defeat the defending champion and world number one in a 6-3 6-4 triumph.

Barty, who had a bye in the first round, did have opportunities, breaking in the first game of the match and building a 4-1 lead in the second set.

But on both occasions Collins stormed back, claiming her first win in four attempts against home favourite Barty, who had beaten her in the semi-finals of last year's tournament.

Coco Gauff continued her fine run to reach a first WTA quarter-final since August 2020 with an impressive comeback win over sixth seed Petra Martic.

The American triumphed 5-7 6-3 6-4 in two hours and 12 minutes to book a clash with compatriot Shelby Rogers at the WTA 500 event.

Gauff did not relinquish serve once after losing the first set and did not even offer up a break-point chance in the decider, which she sealed with a pivotal early break secured with a passing winner.

"I go into every tournament thinking that I can win," said the 16-year-old.

"Obviously that's impossible, to have a perfect record, but I go into every tournament believing that I can win. 

"I try not to think far ahead in the match, at least I just try to focus on my next match, just because you have to get through that before you can get to the finals, and just take it one match at a time."

Second seed Belinda Bencic will face Storm Sanders in the quarter-finals after a 6-1 6-3 win over Misaki Doi.

In a match where she was not quite as dominant as the scoreline suggests, Bencic had to fend off 12 break points but was successful in saving 10 of them.

Number four seed Elise Mertens withdrew before her match with a shoulder injury, so Anastasija Sevastova beat lucky loser Christina McHale to set up a last-eight tie with Jil Teichmann.

World number one Ash Barty refused to criticise Karolina Muchova's reasoning for a medical timeout after she was surprisingly beaten in the Australian Open quarter-finals.

Barty's bid to become the first Australian woman to win the Melbourne grand slam since 1978 came to a shock end on Wednesday, upstaged by 25th seed Muchova 1-6 6-3 6-2.

Winner of the 2019 French Open, Barty raced through the opening set in 24 minutes and led 2-1 in the second before Muchova requested an off-court medical timeout on Rod Laver Arena.

It was a turning point, Muchova returning reinvigorated as the unheralded Czech reached her maiden major semi-final in remarkable fashion, with the 24-year-old revealing during her on-court interview, "I was a bit lost [gestures at head] on the court and my head was spinning so I took a break. It helped me.

"It was more they just checked my pressure because I was a bit lost. I was spinning. So they cooled me down a bit with ice and it helped me."

Asked about Muchova's actions, Barty told reporters: "It's within the rules. She's within her rights to take that time. If she wasn't within the rules, the physios and the doctors would have said so. That's the laws of our game, is that we have those medical timeouts for cases that are needed. Obviously she needed that today. Completely within the rules for her to take that.

"From my point of view, I've played a lot of matches where there have been medical timeouts. I've taken medical timeouts myself before, so that shouldn't be a massive turning point in the match. I was disappointed that I let that become a turning point. I'm experienced enough now to be able to deal with that. It's a disappointment today without a doubt. But we learn and we move on."

Barty added: "I would have liked to have just been a little bit sharper the next game. Started well with the first point, just made a couple loose errors in that game. I think for the rest of the set, that was the story, it was just over and over-made. Probably pressed a little bit trying to be overly aggressive.

"Had some break points, I think it was that three-all, that was probably a bit of a critical game in the momentum there for the second set. Just disappointed with the fact that I wasn't able to bring the match back on my terms after she took that break."

"I didn't hear what she said when she called for the trainer," Barty continued. "That's not my decision. When you call for the trainer, you obviously tell the umpire what the reason is. And then the doctor and physios come out and assess it. That's within the rules. For me, that's not really my decision and not my concern what she took the medical for.

"Obviously there are rules when we go off the court for whatever areas you're getting treated because that's quite normal. But, yeah, that's not really my decision to make on whether or what her medical condition was or what the timeout was for."

Brady, who tallied 31 unforced errors in the final two sets having only managed six in the first, said: "It's heartbreaking, of course. But will it deter me, will it ruin the fact we've had a really successful start to our season? Absolutely not.

"The sun will come up tomorrow. We go about our work again. You're either winning or you're learning. I think today is a massive learning curve for me, for Tyz [coach Craig Tyzzer], my team as well. We take the positives out of it, without doubt and don't let this particular match, this particular hour of tennis deter us from what we're trying to do."

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