The tennis season has begun with Rafael Nadal, Ash Barty, Paula Badosa and Thanasi Kokkinakis among the champions at small-scale events in Australia.

Yet there has been one dominant story in the sport and little else has had a look-in in the lead-up to the Australian Open.

Now that Novak Djokovic knows his fate, there is the welcome prospect of eyes turning to matters on the tennis court, rather than the Federal Court.

With the action getting under way in Melbourne on Monday, Stats Perform looks at the main protagonists and what the numbers tell us about another high-stakes grand slam.

Djokovic absence blows open men's draw

As defending champion Djokovic heads for home, it is worth a reminder of how he has dominated this tournament.

Nine of his grand slam titles have come in Melbourne, and he has taken the trophy in each of the last three years, helping him cosy up alongside Roger Federer and Rafael Nadal on 20 majors, an all-time record they share. Of the 'Big Three', only Nadal is in the draw this year, with Federer currently on the injured list.

Djokovic has the highest win percentage in the Open Era (since 1969) at the Australian Open, among players with 20 or more wins (91.1 per cent – W82 L8). He was hoping to join Nadal (13 French Opens) and Margaret Court (11 Australian Opens) in the exclusive club of players to reach double figures for singles titles at one slam.

The Serb was also aspiring to become the first man in the Open Era to win four consecutive Australian Opens. It happened once before the tour turned professional, with Roy Emerson winning five in a row from 1963 to 1967. Djokovic has left Melbourne with the title every time that he has made it through to the semi-finals.

So who takes the title now?

Only Bjorn Borg (89.2 per cent) has a higher winning percentage in grand slam matches than Nadal (87.7 per cent) and Djokovic (87.5 per cent) in the Open Era, among players with 100 or more wins. So why not Nadal?

The 35-year-old and Djokovic have carved up 12 of the last 14 grand slam titles, Nadal winning four of those (three French Opens, one US Open). He is battling back from a foot injury lay-off and coronavirus, and might need to get the early rounds out of the way without undue stress to stand a chance at the business end.

The two exceptions in the Nadal-Djokovic sequence of slam dominance have come at the US Open, with Dominic Thiem winning in New York in 2020 and Daniil Medvedev triumphing at Djokovic's expense in last year's Flushing Meadows final. Thiem is not in Australia, but world number two Medvedev is, looking to become the third Russian man to win two slams, after Yevgeny Kafelnikov and Marat Safin.

The last man other than Federer, Nadal and Djokovic to secure back-to-back slam singles title was Andre Agassi (US Open 1999 and Australian Open 2000), but that is Medvedev's objective now, and he has the game to pull it off.

Nadal has reached at least the quarter-final stage in 15 of his last 16 grand slam appearances, winning six of those majors (four French Opens and two US Opens), so he may well be a factor.

Who else is in the frame? Alexander Zverev probably, having reached the quarter-finals in Australia in the last two seasons (SF in 2020 and QF in 2021). He won the Olympic Games and ATP Finals titles last year, so a grand slam is an obvious next step. He might want to keep double faults in check though, having served a tour-high 113 in slams last season.

Stefanos Tsitsipas reached the Australian semi-finals in 2019 and 2021, so throw him into the mix too, and Matteo Berrettini might be a threat. The Italian, a runner-up to Djokovic at Wimbledon in July, served more aces than any other player in grand slams last year (311 aces, 16.4 on average per match).

Others have more modest ambitions

Andy Murray is back at the Australian Open for the first time since 2019, when he lost in the first round against Roberto Bautista Agut in five sets and was more or less given his last rites as a tennis pro after the match, having indicated he was close to retirement.

The five-time Australian Open runner-up last won a match in this tournament in 2017, when he reached round four. A tough opener against Nikoloz Basilashvili awaits.

Spanish 40-year-old Feliciano Lopez will make his 80th appearance in a grand slam and become the second man in the Open Era with 80 or more appearances at the four majors, after Federer (81).

Do not expect an Australian to be men's champion, by the way. The last time an Australian reached the men's singles final was 2005, when Lleyton Hewitt lost against Safin, and the last home champion was Mark Edmondson in 1976.

Barty backed in stacked women's draw

For the first time since 1997, neither Serena nor Venus Williams will take part in the Australian Open. Yet the women's tour is in rude health, even without those great bastions.

Ash Barty is world number one and a standout pick for many, only enhancing her claims after winning an Adelaide International title in the run-up to this fortnight.

But there is staggering depth on the women's side at present, and Barty will face stiff competition.

Incredibly, the last five grand slam finals have featured 10 different women, and teenager Emma Raducanu's against-all-odds US Open triumph in September shows best of all that new stars are emerging.

Yet since 2000, only three non-seeded players have reached the women's singles final at the Australian Open: Serena Williams in 2007, Justine Henin in 2010 and Garbine Muguruza in 2020. 

Barty could become the first Australian to be women's champion since Chris O'Neil in 1978, and the first to reach the final since Wendy Turnbull lost to Hana Mandlikova in 1980.

The Queenslander is the top seed, and the last time the number one failed to reach at least the fourth round at Melbourne Park was in 1979, when Virginia Ruzici lost her opening match. Barty ended a long wait for an Australian winner of the women's title at Wimbledon last year, so why not closer to home as well?

Naomi Osaka is back, so what should we expect?

Truth be told, that's hard to know. Osaka took time out from tennis after the US Open to focus on her mental health and enjoyed hanging out with friends, before deciding she missed tennis enough to go back on tour.

She had three wins at the Melbourne Summer Set tournament recently before withdrawing from a fourth match, saying her body had "got a shock" from the intensity. As defending champion in the season's first major, she has a target on her back and will need to find a way to handle that.

Over the past six seasons, only Osaka has managed to win back-to-back grand slam singles titles among the women, and she has done so twice (US Open 2018 and Australian Open 2019, plus US Open 2020 and Australian Open 2021).

The last player to win back-to-back women's Australian Open singles titles was Victoria Azarenka (2012 and 2013), so it does not happen regularly.

Osaka has an 85 per cent win rate at this tournament: since 2000, only Jennifer Capriati (90 per cent) and Serena Williams (89 per cent) have had a higher win percentage in the main draw.

You want challengers to the big two? Try sticking a pin in the draw

The Daphne Akhurst Memorial Cup, which goes to the champion, is a trophy that upwards of a dozen women will seriously believe they can win.

Aryna Sabalenka has reached the semi-finals of the last two slams but is mired in some kind of hellish serving groove, having made 74 double faults in her last four matches and lost the last three in a row.

Anett Kontaveit won a tour-high 39 matches on hard courts last year but has only been to one grand slam quarter-final – last year in Australia, losing to Simona Halep.

What about Ons Jabeur, who matched Kontaveit for a tour-high 48 wins across all surfaces last year? The Tunisian is queen of the drop shot, making 147 successful such plays on tour last year, more than any other player, and recently reached the top 10 in the WTA rankings for the first time.

Maria Sakkari reached two slam semi-finals last year, the first of her career, and the form of Barbora Krejcikova and Badosa in the past week in Melbourne marks them out as contenders. Both are recent fast-risers, Krejcikova already with a French Open title to show.

WTA Finals champion Muguruza could be the second Spaniard to twice reach the Melbourne title match, after Arantxa Sanchez Vicario (1994 v Steffi Graf and 1995 v Mary Pierce). Spain has never had an Australian Open women's singles winner: former French Open and Wimbledon champ Muguruza is an authentic contender.

Halep was runner-up to Caroline Wozniacki in 2018, a semi-finalist in 2020 and quarter-finalist last year, and a Melbourne Summer Set title was a handy warm-up for the Romanian. Consider her, too.

Monica Seles, in 1991, was the last player to triumph on her debut in the main draw, but she was already a grand slam winner (1990 French Open). Given the strength of the line-up, the prospect of a bolter coming through this field is unlikely, even if the example of Raducanu tells us anything is possible.

Ash Barty defeated Elena Rybakina in straight sets to claim the Adelaide International title, while Simona Halep clinched silverware in Melbourne.

World number one and heavy favourite Barty prevailed 6-3 6-2 against Rybakina to claim the Adelaide title for a second time in three seasons.

The 25-year-old recovered from 40-15 down in the seventh game and went on to immediately earn the only break of the opening set.

Barty did not look back as she held throughout the second set, meaning she went 35 consecutive games without losing serve to conclude the tournament.

After securing a 14th WTA singles title in a little over an hour, Barty now turns focus to next week's Sydney Tennis Classic ahead of beginning her Australian Open campaign.

"I feel good leading up to an Australian Open like I have every year," Barty, who hit 17 winners to 13 unforced errors, said after seeing off Rybakina. 

"Each and every preparation is unique. We take it for what comes and what it is, move on, try and do the best that we can in every opportunity.

"It has absolutely no effect on the way that I prepare or the way I'm thinking leading forward just because it's a Grand Slam. It doesn't change for us."

Halep, one of Barty's likely rivals for the Australian Open crown, also made a bright start to the year by overcoming Veronika Kudermetova in the Melbourne Summer Set 1 final.

The number two seed, who is aiming to put last year's injury-ravaged and trophyless season behind her, came out on top 6-2 6-3.

She recovered from an early break down in the first set and again in the second to make it 23 career titles, and a first since the 2020 Italian Open.

It could easily have been a different story, however, as Kudermetova had three break points to move 3-0 ahead in the second set, but the Russian could not take full advantage.

Amanda Anisimova defeated Aliaksandra Sasnovich at the Melbourne Summer Set 2 final to claim the first WTA title of the season, and her second overall.

Belarusian qualifier Sasnovich hit back in style to take the second set 6-1 after losing the opener 7-5, but Anisimova recovered from a break down to edge the deciding set 6-4.

In doing so, Anisimova became the first American to win a title on Australian soil since Sofia Kenin's Australian Open triumph in 2020.

Naomi Osaka will be hoping to be fit for the Australian Open after the reigning champion withdrew from the Melbourne Summer Set 1.

Osaka, who won the most recent of her four grand slam titles last year at Melbourne Park, has looked in fine form this week in her first appearances since returning from the break she took from tennis last year.

The top seed beat Alize Cornet, Maryna Zanevska and Andrea Petkovic en route to the semi-finals, but could not compete against Veronika Kudermetova on Saturday, citing an abdominal injury.

Osaka explained that her body had taken a hit from playing such intense matches in consecutive days, and she instead is looking to rest and recover ahead of the first grand slam of the season, which starts on January 17.

"Sad to withdraw due to injury from my match today, my body got a shock from playing back to back intense matches after the break I took," Osaka tweeted.

"Thank you for all the love this past week [Red heart] I’ll try to rest up and I’ll see you soon!"

Osaka's injury has prevented what looked to be an enticing showdown with Simona Halep, who guaranteed a place in a WTA Tour singles final for a 13th successive season by beating Chinese teenager Zheng Qinwen 6-3 6-2.

Halep's first final came in 2010 and she has taken just a week to get back into her stride after an injury-ravaged 2021 season.

The Romanian, a two-time grand slam champion, went into the week ranked at world number 20, her lowest position at the start of a season since 2013.

However, she has now reached at least the semi-final stage in three successive tournaments, and she will fancy her chances against third seed Kudermetova, who is into her third singles final.

Ash Barty set a new personal best for aces in a match as she rifled 17 past Sofia Kenin on the way through to the Adelaide International 1 semi-finals.

Reigning Wimbledon champion Barty won 31 of 32 points on first serve in a ruthless 6-3 6-4 victory over the 2020 Australian Open winner.

It sets up a tantalising last-four clash with Poland's defending champion Iga Swiatek, who is a frequent practice partner for Australian home favourite Barty.

Explaining her stunning serving performance, Barty said: "I think towards the end Sofia was kind of leaning one way or the other, and I was able to kind of get up and hit my spots."

Facing former French Open winner Swiatek will be a major early-season test for the world number one, with the Warsaw-born 20-year-old fending off former grand slam winner Victoria Azarenka 6-3 2-6 6-1 in Friday's quarter-final.

The other semi-final in Adelaide will see Misaki Doi take on Elena Rybakina after both won in three sets to get there, seeing off Kaja Juvan and Shelby Rogers respectively.

Melbourne Park is staging two tournaments this week, and there is the prospect of a starry final in Melbourne Summer Set 1, with Naomi Osaka and Simona Halep both through to the last four.

Top seed Osaka beat experienced German Andrea Petkovic 6-1 7-5, while second seed Halep had to scrap for a 6-2 5-7 6-4 win against Viktorija Golubic of Switzerland.

Osaka took inspiration from Petkovic's fight in the second set of their contest. Quoted on the tournament website, she said: "It was really cool how she didn't give up for any point, so I just felt like I should do the same thing and see what happens."

Halep said her encounter with Golubic had been "really difficult", adding: "I didn't really trust that I can win this match, but I fought to the end, and I'm very proud of this."

Saturday's semi-finals of Melbourne Summer Set 2 will seed Daria Kasatkina take on Amanda Anisimova, while Ann Li plays Aliaksandra Sasnovich.

Ash Barty produced an impressive comeback to defeat Coco Gauff in her first singles match since the US Open.

World number one Barty moved into the quarter-finals of the Adelaide International with a battling 4-6 7-5 6-1 triumph.

The home hope, who is favourite to win the Australian Open when it starts later this month, was a set and a break down against the American wonderkid before ultimately progressing in two hours and 12 minutes.

Exhausted after a six-month road trip that included Wimbledon glory last year, Barty took a break from the WTA Tour after her third-round exit at Flushing Meadows on September 5.

Her return came in a marquee matchup at the WTA 500 event which did not disappoint, as Barty battled to win 11 of the last 13 games and prevail.

The victor stemmed the early errors she was making on the forehand side, with Gauff paying the price for only converting three of her 15 break-point opportunities. 

It was only the second meeting between Barty and Gauff, with the Australian having to retire with an arm injury while leading their first encounter in Rome last year.

"I felt like I played a pretty good quality match considering it was my first match in a few months," said Barty.

"In the first set I was able to create opportunities but just was a little bit slack on the execution, rusty in the sense of stringing quality points together.

"Midway through the second set I was able to find my rhythm a little bit better on serve and just continued to be aggressive on my forehand. I just found execution a little bit more.

"Coco played great and forced me to hit a lot of balls. I felt I got better and better as the match went on. It was nice to get some court time."

An intriguing last-eight tie lies in wait for Barty. She will either play former Australian Open champion Sofia Kenin or compatriot Ajla Tomljanovic.

And there was more good news for Barty as two of her main rivals for glory were eliminated.

Second seed Aryna Sabalenka was surprisingly beaten as Kaja Juvan, the world number 100, prevailed 7-6 (8-6) 6-1.

Maria Sakkari, the third seed, also crashed out, beaten in three sets by Shelby Rogers, the player who knocked Barty out of the US Open the last time the Australian was on court.

There are two other tournaments taking place this week, both at WTA 250 level.

At Melbourne Summer Set 1, second seed Simona Halep joined Naomi Osaka in round two with a routine 6-4 6-2 win over Destanee Aiava.

The field is not as strong at Melbourne Summer Set 2, where the highest seed remaining, Daria Kasatkina, progressed after opponent Anna Kalinskaya, having already lost the first set, withdrew through injury.

World number one Ash Barty will start her 2022 season at the Adelaide International along with eight of the other current 10 top players in the world.

Barty has held top spot in the women's rankings since September 2019 and collected five titles – including Wimbledon – in the 2021 season but missed the French Open with a hip injury.

She also opted to not play in the season-ending WTA Finals in Mexico due to coronavirus-enforced quarantine concerns that could disrupt her preparation for the following campaign.

The Women's Tennis Association (WTA) confirmed on Friday that Barty would begin her 2022 season in Adelaide on January 2, along with defending champion Iga Swiatek, WTA Finals victor Garbine Muguruza and Roland Garros winner Barbora Krejcikova, as the world's elite players prepare for the Australian Open.

The entry list for the WTA 500 tournaments also includes Tokyo Olympics gold medallist Barbara Bencic, who finished runner-up to Swiatek in 2021, former world number one Karolina Pliskova and US Open runner-up Leylah Fernandez.

The field boasts 12 major trophies between them, but three grand slam winners will kick-start their seasons in Melbourne the day after.

Naomi Osaka, who is aiming to defend her title at the Australian Open, gets her preparations underway in the Melbourne Summer Set.

Two-time major winner Simona Halep and reigning US Open champion Emma Raducanu will play in the Melbourne Summer Set.

The trio are among 20 of the top 50 ranked players in the world for the two WTA 250 tournaments starting on January 3, with the entry list split between the competitions the week before matches start.

Raducanu will feature in just her eighth Tour-level event, and her fourth tournament since winning her first major, while Osaka will be appearing for the first time since an early defeat in the third round of the US Open to Fernandez.

Anett Kontaveit failed to read the script as she beat Simona Halep to win the Transylvania Open and qualify for the WTA Finals for the first time.

Kontaveit went into Sunday's final knowing victory over top seed Halep would earn her the last place in the season-ending tournament in Guadalajara.

The Estonian duly denied Ons Jabeur a WTA Finals spot, beating Romanian home favourite Halep 6-2 6-3 in Cluj.

Second seed Kontaveit has now come out on top in 10 consecutive matches, having won the Kremlin Cup last weekend, and this was her fourth title of a stellar season.

Halep had not dropped a set in her previous three meetings with Kontaveit, but the former world number one was soundly beaten to miss out on a fourth title on home soil – five years after her last in Bucharest.

The 25-year-old Kontaveit took her run to 26 victories in her last 28 matches, winning 70.6 per cent of points behind her first serve to Halep's 44.1 per cent.

Kontaveit broke three times in a one-sided first set and fought back from 2-0 down in the second to continue her brilliant run.

Halep has not won a title since September 2020, having been unfortunate with injuries this year.

Simona Halep progressed to her first final of 2021 as she thrashed Marta Kostyuk to reach the showpiece at the Transylvania Open.

Halep has now reached a WTA final in 12 consecutive seasons after easing to a 6-0 6-1 victory over her teenage opponent.

The two-time grand slam champion faced Kostyuk at Indian Wells three weeks ago and was forced to come from a break down in the first set before prevailing in straight sets.

No such recovery effort was required in Cluj, with Halep progressing to her third final in Romania having twice won the Bucharest Open.

"I really wanted to play the final here. It's a home tournament and always when I come here, I feel great," Halep said. 

"I'm really happy, motivated and I'm looking forward to playing the final tomorrow.

"I knew that I had to play a little bit faster, more aggressive and to open the court a little bit more. There [at Indian Wells], she didn't miss very much as she did today, but I think I took the ball faster and quicker, and the serve helped me today."

"I'm just trying to give my best, trying to be aggressive and enjoy. When I smile inside, it looks better outside. I have the whole country with me when I play at home, so that's why I'm motivated, that's why I feel safe and strong on the court, and I always want to play my best.

"I won twice in Bucharest and, hopefully, tomorrow's the lucky three, but if not, it's still a good result and it's good to be home." 

Halep is unlikely to have it so easy in the final, which sees her face the in-form Anett Kontaveit, who will have added motivation on Sunday.

Kontaveit needed just over an hour to defeat Rebecca Peterson 6-3 6-2, her 25th win in her last 27 matches.

Victory over Halep would see Kontaveit beat Ons Jabeur to the eighth and final spot at the WTA Finals in Guadalajara. However, Halep has won all three of their previous meetings.

At the Courmayeur Open, Clara Tauson will face Donna Vekic in the final after they overcame Liudmila Samsonova and Jasmine Paolini respectively.

Emma Raducanu's hopes of facing idol Simona Halep in the semi-finals of the Transylvania Open were brutally ended by a crushing defeat to Marta Kostyuk on Friday.

US Open champion Raducanu claimed her first ever regular WTA Tour win in Cluj earlier this week, with the 18-year-old keen to impress in the homeland of her father, but Kostyuk denied her the chance of a dream last-four clash with Halep.

The 19-year-old Ukrainian swept Raducanu aside in just 57 minutes, winning 6-2 6-1 as Kostyuk furthered her own burgeoning reputation in the game by reaching a third semi-final of the year.

Raducanu proved her own worst enemy, her 41 unforced errors more than double Kostyuk's 16, with the latter feeling confident as early as the first game when two double faults helped her break the Briton's serve.

"I don't know how I won the first game, I think that's where everything started," Kostyuk said. "I somehow won that game and I gained this confidence, like I'm not going to lose this match.

"After that, by the fifth game maybe, I figured out how to play her – today. Maybe next time I play it's going to be different tactics."

Top seed Halep enjoyed a similarly straightforward victory as she lost just two games en route to a 6-1 6-1 win over Romanian compatriot Jaqueline Cristian, a particularly impressive feat given she had been suffering with a back injury this week.

That success preserved Halep's 100 per cent record against fellow Romanians.

On the other side of the draw, second seed Anett Kontaveit was also an impressive winner as she disposed of Anhelina Kalinina 6-1 6-3 in just over an hour. Kontaveit has won 24 of her last 26 matches and will be the firm favourite against unseeded Rebecca Peterson, who beat Lesia Tsurenko 6-2 3-6 6-3.

At the Courmayeur Open in Italy, third seed Liudmila Samsonova cruised into the semis thanks to a swift 6-1 6-2 demolition of Anna Kalinskaya. She will meet Clara Tauson – seeded fifth – after the Dane came through a more gruelling 3-6 6-4 6-2 win over Ann Li.

The other semi will be contested by Donna Vekic and Jasmine Paolini, who were straight-sets winners over Wang Xinyu and Dayana Yastremska, respectively.

Emma Raducanu is on course to face her idol Simona Halep for the first time in the Transylvania Open after they both advanced to the quarter-finals on Thursday. 

Raducanu celebrated her first WTA Tour win at the expense of Polona Hercog in Cluj on Tuesday and followed that up with a 6-3 6-4 defeat of Ana Bogdan. 

The 18-year-old US Open champion had a first-serve percentage of 69 and won 87 per cent of those points, breaking three times to move into the last eight. 

Third seed Raducanu said: "It's definitely taking me some time to find my feet still. I'm just taking some learnings from every match that I play. I don't think I'm the finished product yet." 

Next up for the Brit is a meeting with fellow teenager Marta Kostyuk after the sixth seed sent Mona Barthel packing with a 6-4 6-4 victory. 

Halep was troubled by a back injury in a 6-4 6-2 success over Varvara Gracheva in her homeland. 

The two-time grand slam champion played through the pain barrier, breaking twice in each set to progress, and could face Raducanu if she beats fellow Romanian Jaqueline Cristian. 

"The back got blocked and the pain is really big," Halep said in the on-court interview. "You cannot really bend much and you cannot move. 

"But sometimes you are used to the pain, I had this before many times, and I just wanted to continue and finish this match. It's good that I won this match, I don't know how." 

Anett Kontaveit, striving to secure a WTA Finals berth, extended her indoor winning run to 12 matches by seeing off Alison Van Uytvanck 6-3 6-4, while Rebecca Peterson knocked Irina Bara out in straight sets. 

In the Courmayeur Open, Jasmine Paolini came out on top 6-4 7-5 in an all-Italian battle with Lucrezia Stefanini and Zhang Shuai got past Wang Xinyu 7-6 (7-5) 6-4. 

The unseeded Donna Vekic also secured a place in the quarter-finals. 

Simona Halep eased to victory over compatriot Elena-Gabriela Ruse on home soil in Romania to advance through to the last 16 of the Transylvania Open.

Ruse won her first WTA title at the Hamburg European Open in July and reached the final of the Palermo Ladies Open later that month, but she was second best against Halep.

The top seed produced a commanding performance as she held serve throughout and broke her opponent twice in both sets to progress 6-1 6-2 in a time of 73 minutes.

Halep, who departed at the quarter-final stage of the Kremlin Cup last week, is on course to meet US Open winner Emma Raducanu in the semi-finals in Cluj.

Anett Kontaveit also prevailed on Wednesday with a straight-sets win of her own, the second seed seeing off Aleksandra Krunic 6-3 7-5.

The 25-year-old, seeking her third WTA 500 indoor trophy in the space of two months, made the most of some Krunic errors to set up a last-16 tie with Alison Van Uytvanck.

Anhelina Kalinina earlier beat Anna-Lena Friedsam 6-2 6-2 to become the first player to book their place in the quarter-finals.

At the Courmayeur Open in Italy, top seed Dayana Yastremska required three sets to overcome Kateryna Kozlova 6-1 3-6 7-5.

Clara Tauson and Ann Li also avoided upsets as they beat Giulia Gatto-Monticone and Kamilla Rakhimova respectively.

Emma Raducanu collected her first WTA Tour victory as she defeated Polona Hercog at the Transylvania Open in Romania.

Raducanu, who was the surprise US Open champion in September after not dropping a set throughout the tournament, appeared at just her fourth tour-level tournament and came to Cluj as third favourite.

The 18-year-old had lost opening-round matches at previous events in Nottingham, San Diego and Indian Wells.

However, world number 23 Raducanu finally recorded her first victory as she overcame a first-set scare to triumph over Hercog 4-6 7-5 6-1.

In the opening match of Tuesday's fixtures, sixth seed Marta Kostyuk cruised past Bernard Pera 6-3 6-4 to secure her last-16 berth.

Irina-Camelia Begu, ranked one behind Kostyuk for the tournament, did not enjoy similar fortunes as Romanian compatriot Irina Bara triumphed 7-6 (7-2) 0-6 6-4.

Jaqueline Cristian survived a marathon slog against Kaja Juvan as she came from a set down to win 3-6 7-6 (10-8) 7-6 (7-3) and book a second-round meeting with Ajla Tomljanovic.

Number one seed Simona Halep – who departed at the quarter-final stage of the Kremlin Cup last week – plays her first game on home turf on Wednesday against Elena-Gabriele Rusa and could meet Raducanu in the semi-final stages.

Meanwhile, Liudmila Samsonova, the third favourite at the Courmayeur Open, cruised past Stephanie Wagner 6-3 6-0 while seventh seed Jasmine Paolini comfortably dispatched Martina Di Giuseppe 6-4 6-1.

Shuai Zhang, who is the third seed in Italy, also enjoyed a routine victory as she eased past Jessica Pieri 6-1 6-3 after fourth favourite Petra Martic crashed out 3-6 4-6 to Saisai Zheng.

Maria Sakkari admitted she got twitchy before finishing off Simona Halep to reach the Kremlin Cup semi-finals.

The Greek star is chasing what would be just her second career title at WTA level, but the limited silverware belies her growing reputation: Sakkari has shot up to a career-high seventh in the world rankings during her best season on tour.

Looking to finish with a flourish, both in Moscow and next month at the season-ending WTA Finals, Sakkari scored a 6-4 6-4 victory over former world number one Halep on Friday.

The victory sets up a last-four clash with Ekaterina Alexandrova, after the Russian impressed a home crowd by landing a 6-3 6-4 win against top seed Aryna Sabalenka.

Yet Sakkari was almost reeled in by Halep from the point of victory in the second set, being unable to finish off the match on her own serve after building a 5-1 lead. Halep twice broke back, before dropping her own serve.

"It was a very tough match today," Sakkari said in an on-court interview. "It was the first time I'd played Simona, but I knew what to expect: she makes a lot of balls, more than any other player. I had a tough moment in the second set when I was 5-1 up, but finally, I found a way. I got a little nervous, a little bit tired.

"The last couple of months have been tough, I've been travelling a lot so haven't recovered enough. I just tried harder in the last game and just went for it."

Alexandrova's shock win over Sabalenka gave her a sixth career victory over a top-10 player. Second seed Garbine Muguruza followed Sabalenka out of the tournament, walloped 6-1 6-1 by in-form Estonian Anett Kontaveit, who has won 19 of her last 21 matches on tour, including beating Sakkari in the Ostrava final last month.

Kontaveit's semi-final opponent at the WTA 500 event will be Marketa Vondrousova, who claimed a 6-4 6-2 win over Anastasia Pavlyuchenkova.

At the Tenerife Open, Italian Camila Giorgi is the only seeded survivor in the semi-finals. The Italian fourth seed saw off Arantxa Rus 6-1 6-1, with Frenchwoman Alize Cornet and American Ann Li also among Friday's winners at the WTA 250 tournament.

Maria Sakkari secured her place at this year's WTA Finals by progressing to the last eight of the Kremlin Cup in Moscow.

The third seed was on court for just 34 minutes on Thursday as last-16 opponent Anna Kalinskaya was forced to retire through injury at 6-2 1-0 down.

Sakkari has enjoyed a successful year on the WTA circuit, reaching grand slam semi-finals for the first time in her career at the French Open and US Open.

Through to the quarter-finals in the Russian capital, where she will play Simona Halep, the 26-year-old becomes the first Greek woman to qualify for the year-end WTA Finals in Mexico.

Eighth seed Halep beat Veronika Kudermetova 6-1 7-6 (7-4), while world number 35 Marketa Vondrousova also prevailed in straight sets against Ukrainian Lesia Tsurenko.

Elsewhere, Ostrava Open champion Anett Kontaveit is through to her eighth quarter-final of 2021 after defeating Andrea Petkovic 6-1 6-4.

Meanwhile, at the Tenerife Open, fourth seed Camila Giorgi enjoyed a commanding 6-1 6-2 victory over Montenegro's Danka Kovinic.

However, there was no joy for seventh seed Clara Tauson as the Danish teenager went down 7-6 (7-4) 2-6 6-4 against China's Saisai Zheng.

Simona Halep reached the second round of the Kremlin Cup on Tuesday with a straight-sets win over home hope Anastasia Potapova.

The former world number one, competing at the Moscow event for the first time since 2013, won 6-1 6-4 to set up a meeting with Veronika Kudermetova, who survived a marathon contest with qualifier Oksana Selekhmeteva.

Anett Kontaveit, who won the title in Ostrava last month, prevailed 6-3 6-3 against Katerina Siniakova. Another seed, Wimbledon quarter-finalist Ons Jabeur, retired against Ekaterina Alexandrova when trailing 6-1 1-0.

Andrea Petkovic also progressed when Jelena Ostapenko had to halt proceedings in their third set, while seventh seed Elena Rybakina lost in straight sets to Olympic silver medallist Marketa Vondrousova.

At the Tenerife Open, Camila Giorgi progressed past Aliona Bolsova 7-6 (7-4) 3-6 6-4 despite giving up two penalty games due to repeated indiscretions when line calls were called into question.

Fifth seed Viktorija Golubic lost in straight sets to Arantxa Rus, while Alison Riske was dispatched 6-1 6-4 by Donna Vekic.

Seventh seed Clara Tauson defeated Heather Watson via a final-set tie-break, while Varvara Gracheva won in the same vein against third seed Sara Sorribes Tormo in a match lasting nearly three and a half hours.

Top seed Elina Svitolina was one set up against Maria Camila Osorio Serrano when their match was suspended for the night.