Naomi Osaka's title defence at her home Pan Pacific Open event came to a premature end as she withdrew from her second-round match against Beatriz Haddad Maia.

The former world number one, who won the Tokyo tournament when it was last held in 2019, was unable to compete in Thursday's match due to illness.

"I am really sorry that I am not able to compete today," Osaka said. "It's an honour to be able to play at the Pan Pacific Open in front of the amazing fans here in Japan.

"This has and always will be a special tournament for me and I wish I could have stepped on court today, but my body won't let me."

Haddad Maia advanced on a walkover and will next face fourth seed Veronika Kudermetova, who defeated Mexican qualifier Fernanda Contreras Gomez 6-0 6-1 to reach the quarter-finals.

Liudmila Samsonova also progressed to the last eight, with a 7-6 (7-5) 6-3 win over Wang Xinyu continuing her good form.

However, sixth seed Karolina Pliskova exited the competition on Thursday at the hands of Petra Martic, who prevailed 6-3 6-4 and will face Zhang Shuai next.

At the Korea Open, top seed Jelena Ostapenko recovered from two games down in the deciding set to overcome Anastasia Gasanova 6-3 5-7 7-5.

Ostapenko remains on a possible semi-final collision course with Emma Raducanu, who came through 6-4 7-5 against Yanina Wickmayer, while Magda Linette saved two match points to beat Kristina Mladenovic 4-6 7-6 (7-5) 6-2.

The top two seeds were eliminated in the second round of the Pan Pacific Open in Tokyo as Paula Badosa and Caroline Garcia both crashed out on Wednesday.

Badosa was defeated in just 78 minutes by Zheng Qinwen, with the number one seed going down 6-3 6-2.

It was 19-year-old Zheng's first completed win against a top 10 opponent in her career, and she said afterwards: "Even though the score was like this, there were a lot of emotions for me in this match and I'm very proud of myself. It's not a surprise. I always knew I had the level, I just had to make it."

Second seed Garcia hit 27 aces in her match against Zhang Shuai, the most in a single WTA-level contest since Kristyna Pliskova against Monica Puig in Luxembourg 2019 (28), but it was not enough as she lost two tie-breaks to lose 4-6 7-6 (7-5) 7-6 (7-5).

Number three seed Garbine Muguruza had more success as she beat Greek opponent Despina Papamichail 6-4 6-2, while Claire Liu also eased to a win against Elise Mertens 6-4 6-1, and will play Zheng in the quarter-finals.

Eighth seed Elena Rybakina suffered a first-round exit as she lost to Liudmila Samsonova 6-2 6-4, who will play Xinyu next.

The seeds fared better over at the Korea Open, with Emma Raducanu sealing a first-round win against Moyuka Uchijima 6-2 6-4, while Magda Linette also eased past Arianne Hartono, 6-2 7-5, though fifth-seed Varvara Gracheva was knocked out by Anna Blinkova 6-4 7-6 (7-1).

In the second round, third seed Ekaterina Alexandrova is through after beating Han Na-lae 6-1 6-3, as is Lin Zhu of China following her straightforward 6-1 6-3 victory against India's Ankita Raina.

There were also wins for Tatjana Maria against Kimberly Birrell, and 17-year-old Andorran Victoria Jimenez Kasintseva against eighth seed Rebecca Marino.

Naomi Osaka began the defence of her Pan Pacific Open crown with a quick win after opponent Daria Saville was forced to retire in just the second game.

Four-time grand slam champion Osaka won the opening game, before Saville was unable to continue due to a scary-looking injury to her left knee.

The former world number one will now face a second round match with world number 16 Beatriz Haddad Maia, who eased to a straight sets victory over Yuki Naito.

Karolina Pliskova secured her place in the next round in Tokyo with a 6-2 6-1 demolition of Isabella Shinikova, while Zhang Shuai will face second seed Caroline Garcia on Wednesday after overcoming Mai Hontama in two sets.

In Seoul, Jelena Ostapenko's hopes of repeating her 2017 heroics at the Korea Open are still alive after the number one seed narrowly beat 19-year-old Jeong Bo-young.

The world number 19 looked to be cruising after the opening set, but the unheralded South Korean hit back in the second and took it to a tie-break in the third, before Ostapenko's class showed as she won the crucial tie-break 7-2.

Elsewhere, 2021's beaten finalist Kristina Mladenovic saw off wildcard Park So-hyun 6-4 4-6 6-3, while second seed Ekaterina Alexandrova overcame a worrying second set to beat Asia Muhammad 6-1 3-6 6-1.

Wimbledon semi-finalist Tatjana Maria is also safely through to the second round after a tight 7-6 (7-5) 7-6 (7-5) triumph over Eugenie Bouchard.

Four-time grand slam champion Naomi Osaka admitted she has not had "the best year" but is still "pretty happy with where I am now."

Osaka – a former world number one – has slipped to 48th in the latest WTA rankings, and has not won a match at a grand slam since she beat Madison Brengle in the second round at the Australian Open in January.

The Japanese-born star was eliminated in the first round at the French Open and US Open this year, and did not compete at Wimbledon due to an Achilles injury.

Having taken some time away from the game last year to focus on her mental health, Osaka has struggled to get back to her previous high levels.

However, speaking ahead of the Pan Pacific Open in Tokyo, she seemed calm about the situation, as she suggested she is improving both on and off the court.

"It was kind of hard at first, just because I feel like I should be somewhere where I'm obviously currently not," the 24-year-old said.

"I think for me, it's more about being at peace with myself. I know that I'm here for a reason."

Osaka has seven career singles titles to her name, including four majors – she has won twice at Flushing Meadows and twice at the Australian Open.

"This year has not been the best year for me, but I've learned a lot about myself," she added.

"Life is ups and downs, and this year was more down than up, but overall I'm pretty happy with where I am now."

She is preparing to defend her title at the Pan Pacific Open, which has not been held in three years due to the coronavirus pandemic, starting with a match against Daria Saville on Tuesday.

"It feels really weird to hear that I'm the defending champion because it was the last time I played in 2019," she said.

"I would love to win it again, but I think just taking it one match at a time... and also just playing in front of a crowd in Tokyo again, because the Olympics was crowdless, so it will just be nice to see people."

Alison Riske-Amritraj suffered another early exit as the Pan Pacific Open began in Tokyo on Monday.

Riske-Amritraj reached the last 16 at the US Open earlier this month but has struggled in Asia since then.

She was the top seed at the Chennai Open last week, only to lose in straight sets in the first round to Anastasia Gasanova.

And the American fell at the first hurdle again in Japan.

Riske-Amritraj was drawn against compatriot Claire Liu, who was coming off back-to-back defeats to Anastasia Potapova and without a win since qualifying for the Canadian Open last month.

But Liu brushed aside the seventh seed 6-2 6-3 to set up a meeting with Elise Mertens in the second round.

Mertens eased through with a 6-0 6-3 win over Wang Qiang, while Petra Martic was similarly comfortable in a 6-1 6-1 defeat of Rina Saigo.

Saigo was one of two home hopefuls to depart on Monday as Qinwen Zheng won 19 points in a row en route to beating Misaki Doi 6-2 6-4.

At the Korean Open, Zhu Lin was the only seed in action and got the better of Jang Su-jeong in straight sets.

Katerina Siniakova ended her five-year wait for a WTA singles title after coming from behind to defeat Elena Rybakina and claim the Slovenia Open crown.

The Czech secured the third singles triumph of her career – and first since prevailing at Bastad in 2017 – as she recovered from losing the opening set to deny Wimbledon champion Rybakina 6-7 (4-7) 7-6 (7-5) 6-4.

Siniakova – also the doubles world number one – continued her rich vein of form, having captured her third grand slam of 2022 alongside Barbara Krejcikova at the US Open last week.

The world number 82 had come through two matches on Saturday to reach the championship match in Portoroz, and was slow out of the blocks as she fell 5-0 behind in the opening set. Although Siniakova fought back to force the tie-break, Rybakina held her nerve by winning four of the last five points to draw first blood.

The Wimbledon champion, who hit 43 winners, appeared to be closing in on victory in her third final of the year as she broke for 4-3 in the second set. However, Siniakova broke back immediately before eventually forcing a decider.

Both players exchanged breaks early on in the third, but Rybakina's increasing unforced error tally (66) eventually culminated in her opponent claiming another crucial one for 5-4, before serving it out to end the drought.

Over at the Chennai Open, teenager Linda Fruhvirtova also enjoyed a comeback victory as she denied Magda Linette 4-6 6-3 6-4 to land her maiden WTA title.

Aged 17 years and 141 days, Fruhvirtova became the youngest winner on the WTA Tour this season, and is set to climb into the world's top 100 for the first time.

In a tight opening set, Linette broke for 5-4 before holding to love to strike first. A solitary break also proved crucial in the second set; the Czech profiting on this occasion to ensure the final went to a decider.

Linette, who won just two out of nine break points, established early control as she surged into a 4-1 lead, but Fruhvirtova came roaring back as she reeled off five straight games to seal a fitting end to her breakthrough week.

Wimbledon champion Elena Rybakina cruised to a straight sets victory over world number 65 Ana Bogdan to secure her place in Sunday's Slovenia Open final.

The Kazakhstan representative broke Bogdan five times while saving all eight break points to seal a 6-1 6-1 triumph and reach a first final since her SW19 victory over Ons Jabeur in July.

In the final, Rybakina will face Katerina Siniakova after she overcame Anna-Lena Friedsam.

Siniakova stormed to the first set, but the second was a much closer affair and the world number 82 watched five match points come and go before she finally clinched a 6-1 7-5 success.

At the Chennai Open, Magda Linette will play Linda Fruhvirtova in Sunday's decider after coming through semi-final encounters in differing fashion.

Third seed Linette raced out to a 3-0 lead in the first set over Katie Swan before the Brit called a medical timeout after just 16 minutes of play, eventually retiring with illness.

Fruhvirtova's semi-final was a much more gruelling affair, as the 17-year-old came from a set down to overcome Nadia Podoroska 5-7 6-2 6-4 and reach her first WTA final.

Qualifier Anna-Lena Friedsam backed up her victory over Emma Raducanu with a 1-6 7-6 (7-4) 6-3 quarter-final win over Diane Parry at the Slovenian Open.

After seeing off 2021 US Open champion Raducanu on Thursday, Friedsam continued her run with a superb comeback win to book her place in the semi-finals.

A rough start looked to have primed Friedsam for the exit door, but after prevailing in the second set, the 28-year-old pushed on to take herself within a match of a third career WTA Tour-level final.

She will have to wait to discover whether she will face defending champion Jasmine Paolini however, with the Italian's own quarter-final in Portoroz against Katerina Siniakova delayed until Saturday.

Third seed Elena Rybakina, meanwhile, will face Romania's Ana Bogdan after the Wimbledon champion was handed a walkover following Lesia Tsurenko's withdrawal.

Bogdan reached her second tour-level semi-final of the season by upsetting second seed Beatriz Haddad Maia, recording her 20th win over a top-20 opponent in the process, albeit her first since the 2018 Australian Open.

At the Chennai Open, 17-year-old Linda Fruhvirtova stunned Varvara Gracheva 6-4 6-3 to reach her first Tour-level semi-final.

Briton Katie Swan continued her impressive run with a 6-3 3-6 6-3 win over qualifier Nao Hibino and she will face Poland's Magda Linette, the highest-ranked player left in the competition, in the last four.

Fruhvirtova will go up against Nadia Podoroska, who came from a set down to defeat Eugenie Bouchard.

Serena Williams has paid tribute to retiring 20-time grand slam winner Roger Federer, describing her admiration for him and welcoming him "to the retirement club".

The 41-year-old confirmed on Thursday that he would bring an end to his illustrious playing career after the Laver Cup later this month.

Federer's announcement comes only weeks after 23-time major winner Williams declared her intention to step away from tennis, culminating at the US Open earlier this month where she bowed out in the third round.

The Swiss icon will bow out with 20 major titles to his name, a feat bettered by only two male players – Rafael Nadal (22) and Novak Djokovic (21). Williams sits behind only Margaret Court (24) for women's singles major titles.

"I wanted to find the perfect way to say this, as you so eloquently put this game to rest – perfectly done, just like your career," Williams wrote on Instagram.

"I have always looked up to you and admired you. Our paths were always so similar, so much the same.

"You inspired countless millions and millions of people – including me – and we will never forget. I applaud you and look forward to all that you do in the future.

"Welcome to the retirement club. And thank you for being you @rogerfederer."

Williams has deliberately avoided the use of the word retirement since declaring her intention to 'evolve' away from tennis, meaning the latter comment is of note.

The 40-year-old American has teased at a potential return to tennis, saying on Good Morning America this week that "Tom Brady started a really cool trend", referencing his decision to come out of retirement.

WTA world number one Iga Swiatek thanked Roger Federer for "everything you've done and everything you are for our sport" after the Swiss great announced his retirement.

Federer confirmed on Thursday that he would bring his illustrious playing career to a close after the Laver Cup.

The 41-year-old will bow out with 20 grand slam titles to his name, a feat bettered by only two male players – Rafael Nadal and Novak Djokovic.

Swiatek, meanwhile, won her third major title last week, defeating Ons Jabeur in straight sets to clinch the US Open, following her successes at Roland Garros in 2020 and earlier this year.

"I just want to thank you for everything you've done and everything you are for our sport," 21-year-old Swiatek tweeted in response to Federer's announcement.

"It's been a privilege to witness your career. I wish you all the best." 

Swiatek followed her post with a goat emoji, signifying that Federer is the greatest of all time.

Chris Evert, a former world number one, also joined the tributes to Federer, tweeting: "He was the epitome of a champion; class, grace, humility, beloved by everyone…and he elegantly mastered the sport like no other…Good luck to you, @rogerfederer don't go too far!"

Martina Navratilova, an 18-time major winner, posted: "What a heartfelt message, full of love, life, hope, passion and gratitude. Which is exactly how Roger played the game we love so much. Thank you thank you thank you, for all the magic!!!"

Emma Raducanu struggled with injury as she slumped out of the Slovenia Open in a second-round 7-5 0-6 6-3 loss to Anna-Lena Friedsam.

The 2021 US Open champion has faced an uphill battle on the WTA Tour this year and suffered another setback in Portoroz, where she was the top seed, playing the latter two sets with her left thigh strapped after a medical time-out.

A recovery looked possible when Raducanu cruised through a second-set bagel, yet the 19-year-old succumbed in the decider.

Raducanu's defeat follows a first-round exit at Flushing Meadows in a dismal attempt to defend her title.

Friedsman's win, meanwhile, secures the world number 213's first appearance in the quarter-finals of a Tour-level event since she lost in the final of the Lyon Open in 2020. It was also her second victory over Raducanu.

Diane Parry will face Friedsman in the last eight, after she overcame Anastasia Potapova, while Katerina Siniakova – who last week completed a career Grand Slam in doubles at the US Open – defeated Jodie Burrage.

Meanwhile, reigning champion Jasmine Paolini overcame a tie-break finale against Kaja Juvan. The Italian fought back to win 5-7 6-2 7-6 (7-5) to stay on course for a successful title defence.

At the Chennai Open, Anastasia Gasanova failed to back up her first-round win over top seed Alison Riske-Amritraj with another success, as Britain's Katie Swan edged her 7-6 (7-5) 6-2.

That sets up a quarter-final clash with qualifier Nao Hibino.

The top two seeds left in the competition, Magda Linette and Tatjana Maria, also progressed on Thursday.

Rafael Nadal says it has been "an honour and a privilege" competing with Roger Federer after the 20-time grand slam winner announced his retirement on Thursday.

In a statement posted on social media, Federer confirmed his "bittersweet decision" to call time on his top-level tennis career after next week's Laver Cup in London.

Federer won 20 grand slam titles across a legendary 24-year career, a trophy tally in majors that only Novak Djokovic (21) and Nadal (22) can better.

The 41-year-old has not competed since Wimbledon 2021, after which he underwent a third knee operation, but Nadal had hoped his fellow great would never retire.

"Dear Roger, my friend and rival. I wish this day would have never come. It's a sad day for me personally and for sports around the world," Nadal posted on his Twitter account.

"It's been a pleasure but also an honour and privilege to share all these years with you, living so many amazing moments on and off the court."

Nadal, who will team up with Federer and Djokovic as part of Team Europe's all-star cast at the Laver Cup, added: "We will have many more moments to share together.

"There are still lots of things to do together, we know that. For now, I truly wish you all the happiness with your wife, Mirka, your kids, your family and enjoy what's ahead of you."

Federer has spent 750 weeks in the top 10 of the men's singles rankings, an undefeated number for a male player since they were first published in 1973.

The Swiss has also won more men's singles main draw matches in grand slam tournaments than any other player in the Open Era (369).

As he brings down the curtain on his remarkable career, several other players paid their respects to one of the sport's all-time greats. 

"Some of Fed’s numbers are laughably impossible to top (23 straight slam semi-finals, for instance)," John Isner posted on Twitter. 

"But his impact on tennis far exceeds what he accomplished on court. Thanks for everything, RF."

Seven-time grand slam winner Petra Kvitova added: "Roger, you have always been such a huge inspiration to me. Your elegance, your grace, your beautiful game. 

"I have always held you in the highest regard and want to congratulate you for an amazing career. Tennis won’t be the same without you! Thank you."

US Open champions past and present Andy Roddick and Carlos Alcaraz led a swathe of social media tributes to Roger Federer after the 20-time grand slam winner announced his retirement.

Federer, who has not played competitively since exiting Wimbledon at the quarter-final stage last year, revealed on Thursday that next week's Laver Cup will be his farewell tournament.

Federer appeared at a parade of former champions at Wimbledon earlier this year and hinted at his desire to feature at the All England Club once more, but his upcoming outing in London will now represent the swansong to his stunning career.

The Swiss great will become the first of the ATP Tour's 'Big Three' to exit the sport, with Rafael Nadal and Novak Djokovic still active. 

While Nadal and Djokovic have each surpassed Federer's tally of 20 major titles this year, the 41-year-old overtook Pete Sampras' previous record of 14 grand slam titles by beating Roddick in the 2009 Wimbledon final.

Roddick was among the first to pay tribute to Federer's achievements on Thursday, writing on Twitter: "Cheers Roger. Thanks for the shared memories my friend. 

"It was an honour to share time/experiences on the most hallowed grounds in our sport. Don't be a stranger."

Alcaraz, who clinched his first grand slam title and became world number one with a US Open final win over Casper Ruud on Sunday, simply wrote: "Roger…", accompanied by a heartbroken emoji.

Milos Raonic has seen his efforts to win a major title foiled by the presence of the 'Big Four' – with Andy Murray beating him on his sole grand slam final appearance at Wimbledon in 2016 – but he also showed his appreciation for Federer's impact.

"Thank you for doing more for tennis than any single individual," Raonic wrote. "Thanks to you competitors and fans across the world get to experience and enjoy it all over the world. 

"Congratulations on your achievements and the people you continue to impact in and away from tennis."

Juan Martin del Potro, who prevented Federer from winning six consecutive US Open titles with a five-set success in the 2009 final, labelled the 41-year-old irreplaceable, declaring: "I LOVE YOU, Roger. 

"Thank you for everything you've done in tennis and with myself. [The] tennis world will never be the same without you."

Former player-turned presenter James Blake added: "Roger, there was and never will be anyone like you. You crushed me on the court, but were so nice and genuine that I couldn't hate you for it. 

"You made the game better on and off the court and you will be missed. Good luck, you have earned all the success and joy in the world."

Garbine Muguruza tweeted: "RF" followed by a heartbroken emoji.

Those who shared a court with Federer were not the only ones to pay tribute, however.

A tweet from Wimbledon's official account read: "Roger, where do we begin? It's been a privilege to witness your journey and see you become a champion in every sense of the word. We will so miss the sight of you gracing our courts, but all we can say for now is thank you, for the memories and joy you have given to so many."

Roland Garros' official account tweeted: "An inspiration on and off the court. Thank you, Roger."

The US Open's handle simply posted: "Thank you, Roger."

Simona Halep has announced her season is over after undergoing nose surgery to address problems with her breathing.

Working with Serena Williams' former coach Patrick Mouratoglou, Halep enjoyed a promising 2022 following an injury-hit 2021 campaign, reaching the semi-finals at Wimbledon and moving up to ninth in the WTA rankings.

However, the two-time major champion has struggled since winning the Canadian Open last month, losing in the first round at the US Open.

Prior to her success in Canada, Halep was forced to retire in the second round of the Citi Open after enduring breathing difficulties, and the ongoing problem prompted surgery this week, with Halep disclosing she also elected for cosmetic changes to the nose.

The former world number one will miss the final events on the WTA Tour this year, but she explained the procedure was necessary.

She wrote on Twitter: "As you all know already because I've talked about it many times, in February, I was very close to stopping tennis because I didn't believe I have enough power to come back to top 10. I was going through many anxious moments and I thought it is time to stop cause it is emotionally unhealthy. 

"Then I was lucky to discover Patrick's academy where I felt so much passion that it gave me back my passion for tennis. Thanks to Patrick, I slowly started to believe that I still can play a good level of tennis.

"My goal was very clear: I gave myself one year to get back to top 10. And faster than I ever expected, in only two months, I was back to top 10. Goal achieved!

"But then, when I lost at the US Open, I realised that I'm completely exhausted mentally. Having problems with the breathing for many years already and becoming worse with the time, I decided to follow the advice of my doctors and do the needed surgery.

"I could never do it earlier because I never found the necessary three months for the recovery, because tennis was always the first priority in my life. But I felt it's the right time to do it and also to do something for myself as a person.

"That is why I did also the aesthetic part, that I wanted to do for a long time as I did not like my nose at all. So I did it, I solved the functional part and the aesthetic part.

"I don't know how long the recovery will take, for the moment I am not thinking about anything but recovery. What is sure, is that this year I won't be able to compete in any official tournament anymore.

"My 2022 season is over. 2022, you have been an interesting year full of everything! See you on court, 2023! I feel I still have a lot to do on a tennis court and still have some goals."

Wimbledon champion Elena Rybakina advanced to the third round of the Slovenia Open after a convincing 6-4 6-1 victory against Tereza Martincova on Wednesday.

Rybakina, who in July became Kazakhstan's first ever grand slam champion, was too strong for her Czech opponent, creating 14 break point opportunities in the match while only facing two herself.

Her first serve accuracy was not great at 52 per cent, but she was devastating when she landed it fair, converting 21-of-24 chances.

Rybakina will face Lesia Tsurenko in the next round after the Ukrainian upset fifth seed Ekaterina Alexandrova 7-5 7-6 (7-5).

Second seed Beatriz Haddad Maia also had no issue navigating the challenge of Cristina Bucsa 6-1 6-4, and she will meet Ana Bogdan in the third round after the Romanian defeated Tamara Zidansek 6-1 6-7 (7-5) 6-1.

Meanwhile, in India at the Chennai Open, popular Canadian Eugenie Bouchard collected consecutive wins for the first time March 2021 following a lengthy recovery from shoulder surgery.

The 28-year-old defeated Karman Kaur Thandi 6-2 7-6 (7-2) as she looks to climb back up the rankings, currently sitting 902nd in the world after peaking at number five back in 2014.

Earlier in the day, sixth seed Qiang Wang was upset by Japanese qualifier Nao Hibino 6-2 6-3, while fifth seed Rebecca Peterson was also eliminated, going down 6-4 6-2 to Linda Fruhvirtova.

Wrapping up the day's action, Canada's Rebecca Marino booked a potential showdown with third seed Magda Linette after beating Poland's Katarzyna Kawa 7-5 6-3.