Stefanos Tsitsipas opened his United Cup campaign with a comeback victory over Grigor Dimitrov in Perth.

ATP world number four Tsitsipas is one of the headline names in action at the event, which is acting as a warm-up tournament for the Australian Open.

After going a set down to his Bulgarian opponent in his first game of the inaugural tournament, Tsitsipas hit back with a strong second set before holding his nerve in a tense tie-break in the decider, securing a 4-6 6-2 7-6 (7-4) win.

Tsitsipas's team-mate Despina Papamichail continued Greece's strong start, also coming from a set down to beat Isabella Shinikova 3-6 6-4 6-1.

Great Britain opened with a pair of victories, Cameron Norrie and Katie Swan earning straight sets triumphs over their Australian counterparts in Sydney.

Norrie, who was initially set to play Nick Kyrgios prior to the Wimbledon finalist's withdrawal due to an ankle injury, eased to a 6-3 6-3 victory over Alex De Minaur, while Swan defeated Zoe Hives. 

The United States are also taking a 100 per cent record into day two of the tournament, after Taylor Fritz and Madison Keys overcame Jiri Lehecka and Marie Bouzkova respectively, while France pair Arthur Rinderknech and Alize Cornet got off to winning starts against Argentina's Francisco Cerundolo and Maria Lourdes Carle.

In Brisbane, Swiss hope Belinda Bencic secured a 7-6 (7-0) triumph over Yulia Putintseva of Kazakhstan and Beatriz Haddad Maia, the Brazilian world number 15, dispatched Italy's Martina Trevisan 6-2 6-0.

It was a great day for the highly ranked Americans at the Guadalajara Open on Wednesday, headlined by world number five Jessica Pegula and her 2-6 6-3 7-6 (10-8) comeback win over Wimbledon champion Elena Rybakina.

Pegula, who is now locked into the top-eight and therefore will qualify for the WTA Finals, struggled to win points on her serve in the opening set, but raised her 57 per cent success rate up to 69 per cent in the second set, and 66 per cent in the decider.

The American had to come from a break down in the second set to keep her tournament alive, and she will now face Canada's Bianca Andreescu in the third round.

Meanwhile, fellow United States star Coco Gauff was too good for Italy's Elisabetta Cocciaretto, winning 7-6 (7-1) 6-3 to book a third-round clash with another Italian, Martina Trevisan, who earned her way there with a 6-0 4-6 6-3 win over Katerina Siniakova.

The other two seeded Americans were also successful, with 13th seed Madison Keys coming from a set down to defeat Ajla Tomljanovic 3-6 6-4 6-3, and 14th seed Danielle Collins repelled the challenge of Magdalena Frech 6-3 6-4.

There were positive signs for former world number five Eugenie Bouchard, who ended up losing, but showed she still has her talent by taking a set off world number 23 Jelena Ostapenko in a 7-5 2-6 6-1 result.

Russian pair Anna Kalinskaya and Liudmila Samsonova both emerged in three-set outings, with Kalinskaya outlasting Elise Mertens 6-4 0-6 7-5, while Samsonova upset world number four Aryna Sabalenka 6-4 2-6 6-2.

World number 12 Veronika Kudermetova kept her WTA Finals hopes alive with a 6-4 7-5 win over Donna Vekic, and the Czech Republic's Marie Bouzkova ousted Colombia's Camila Osorio 6-3 6-1.

In the late window, Sloane Stephens eliminated Olympic gold medalist Belinda Bencic 6-4 6-4, and top overall seed Paula Badosa retired due to injury after losing the first set 6-2 against Victoria Azarenka.

Victoria Azarenka has booked a clash with the top seed of the Guadalajara Open after defeating Elina Avanesyan 6-4 6-2 in Monday's opening round.

In the last event of the season before the WTA Finals, Belarus' Azarenka was too strong with her return game for her Russian opponent, winning 53 per cent (32-of-60) of her return points while capitalising on five-of-seven break point opportunities to earn a shot at world number eight Paula Badosa.

While Azarenka has no chance of qualifying for the WTA Finals – with only the top-eight players in the rankings making it through – Belinda Bencic is one of the players who can sneak in with a great result this week.

Needing to make the semi-finals to have a chance, she got off on the right foot with a 7-5 6-7 (10-12) 6-3 win against Leylah Fernandez in her opening match.

Petra Kvitova can also qualify if she reaches the final, and she started without issue, defeating Bernarda Pera 6-3 7-5.

Ekaterina Alexandrova had an outside chance of claiming a WTA Finals spot if she won this tournament, but she was the victim of the day's biggest upset, falling 6-4 7-6 (10-8) to Camila Osorio.

At 22nd in the world, Liudmila Samsonova is the lowest-ranked player in the field with a mathematical chance at qualification, but she is a step closer after handling Kaia Kanepi 6-1 7-5.

Despite Fernandez's earlier loss, it was a strong day for the Canadians, with Bianca Andreescu proving too good in her 6-2 6-4 victory against Jil Teichmann, and Rebecca Marino also only needed two sets to defeat Ann Li 6-2 7-6 (7-2).

China's Lin Zhu came from a set behind to beat France's Alize Cornet 3-6 6-3 6-4, while Ukraine's Marta Kostyuk had a much quicker result in her 6-1 6-3 triumph over Belarus' Aliaksandra Sasnovich.

World number 34 Elise Mertens had no problems in one of the biggest mismatches of the day as she defeated world number 185 Asia Muhammad 6-3 6-2, and Sloane Stephens needed only 54 minutes to advance 6-0 6-2 past Linda Fruhvirtova.

In the last match of the night, Mexico's top chance Fernanda Contreras Gomez was eliminated by Alja Tomljanovic 6-2 6-1.

Anett Kontaveit and Maria Sakkari were both knocked out of the Ostrava Open on Thursday as several top seeds tumbled.

Third seed Kontaveit, who won this competition last year, retired when a set down to Tereza Martincova, while world number seven Maria Sakkari was defeated 5-7 7-5 7-5 by 21-year-old American Alycia Parks in a big upset.

Parks lost the opener but found two crucial breaks of serve when 6-5 up in both the second and third sets to eliminate the fourth seed.

The withdrawal of Belinda Bencica – seeded sixth – with a foot injury put Barbora Krejcikova into the quarter-finals, while Ekaterina Alexandrova will also be in the last eight after overcoming fifth seed Daria Kasatkina 6-1 7-6 (7-1).

The tournament favourites were in much better form at the Jasmin Open in Tunisia, as the top two seeds sealed their places in the quarter-finals with straight-sets wins.

Favourite Ons Jabeur cruised to a 6-1 6-3 victory over Evgeniya Rodina, converting four of her seven break points to safely advance to the next round of her home tournament.

And number two seed Veronika Kudermetova eased past Magdalena Frech 6-3 6-4 to set up a quarter-final meeting with Diane Parry.

Belinda Bencic fought back to defeat Eugenie Bouchard in an Ostrava Open first-round contest that took over two and a half hours to settle.

Bouchard took the first set, but Bencic came from behind to advance with a 6-7 (7-9) 6-1 6-4 victory on Tuesday.

Eighth seed Jelena Ostapenko, runner-up in the Korea Open, suffered a premature exit as Aliaksandra Sasnovich consigned the former French Open champion to a 6-2 6-2 defeat.

Emma Raducanu also went out in straight sets, with Daria Kasatkina beating the 2021 US Open champion 7-5 6-4.

Catherine McNally blitzed to a 6-1 6-2 victory over Anna Blinkova, while Alycia Parks progressed past Karolina Pliskova to secure the first top-20 win of her career.

Top seed Ons Jabeur swept aside Ann Li with relative ease in a 6-2 6-3 victory at the Jasmin Open to reach the last 16.

Veronika Kudermetova, the second seed, breezed past Varvara Gracheva with a commanding 6-1 6-0 win.

Anastasia Potapova, Petra Martic, Magdalena Frech and Harriet Dart were among the other victors.

Korea Open finalist Jelena Ostapenko was knocked out in the first round of the Tallinn Open after letting a one-set lead slip against Kaia Kanepi.

Ostapenko looked to be cruising after winning the opener, but Kanepi levelled in the second despite the Estonian watching five set points come and go.

Kanepi then romped to victory with a stunning final set to defeat Ostapenko 4-6 6-4 6-0 and keep her hopes of winning her home tournament alive.

In second-round action, Beatriz Haddad Maia is through to the quarter-finals after a 6-1 7-5 success over Linda Noskova.

After Haddad Maia cruised to a one-set lead, the second was a much tighter affair before the Brazilian's class showed as she broke Noskova and then held serve to earn a straight-sets win.

Second seed Belinda Bencic also secured her place in the final eight with a 6-4 6-7 (2-7) 6-3 triumph over Katie Boulter.

At the Parma Ladies Open, top seed Maria Sakkari came from behind to beat Arantxa Rus and seal her quarter-final spot.

Rus saved five out of five break points as she won the opening set 6-3 to give her hope of an upset.

Those hopes were soon dashed though as world number seven Sakkari broke twice to take the second set 6-2, before clinching the match in the third to tee up a clash with Maryna Zanevska.

World number 33 Irina-Camelia Begu made it 12 consecutive wins on clay by overcoming Matilde Paoletti in straight sets and will face fellow Romanian Ana Bogdan in the next round after she beat Anna Karolina Schmiedlova 6-2 3-6 6-3.

Fourth seed Sloane Stephens saw her tournament come to an end after she was defeated by Danka Kovinic.

Maria Sakkari was made to work as she battled her way back from a set down to reach the last 16 of the Parma Ladies Open.

The number one seed lost the first set to Ukrainian qualifier Kateryna Baindl as a shock appeared to be on the cards.

But the two-time grand slam semi-finalist showed great spirit to eventually win 6-7 (7-2) 6-2 6-3 after two hours and 45 minutes on court.

Fourth seed Sloane Stephens also had to respond to first-set disappointment before coming through 3-6 6-3 6-4 against Magdalena Frech.

The only other seed in action on Monday was Ana Bogdan (sixth), and she had no such issues as she lost just three games in a straightforward win over Brazilian Laura Pigossi that took just 73 minutes.

At the Tallinn Open in Estonia, Belinda Bencic was the highest-ranked player on court on Monday, and the second seed breezed through her first-round clash with local favourite Elena Malygina 6-0 6-2.

Karolina Muchova crushed Jessika Ponchet by the same scoreline, while Barbora Krejcikova, seeded seventh, saw off Ajla Tomljanovic 6-1 7-6 (7-3) in straight sets.

However, there was no joy for Madison Keys; the fourth seed going down 6-3 6-2 against Switzerland's Viktorija Golubic.

Marta Kostyuk defeated Bernarda Pera 6-6 4-6 6-3, and Great Britain's Katie Boulter dropped only four games in her 6-3 6-1 demolition of Jaqueline Cristian, setting up a second-round date with Bencic.

Two-time major winner Simona Halep continues to find form ahead of the upcoming US Open with a 6-4 7-6 (7-2) victory over Coco Gauff clinching her spot in the Canadian Open semi-finals.

Halep defeated 10th seed Gauff, who had beaten Naomi Osaka, Elena Rybakina and Aryna Sabalenka this week, in one hour and 47 minutes.

The Romanian 15th seed was broken five times and sent down eight double faults, but found the edge with speed, finesse and power.

The win means Halep has won the third most matches (36-10) on the WTA Tour this season, behind only top-ranked Iga Swiatek (49) and Wimbledon finalist Ons Jabeir (37).

Halep's improved form comes after she teamed up with Serena Williams' ex-coach Patrick Mouratoglou in April following a difficult 2021 season.

"Before I met him I was super down with my motivation," Halep told reporters. "I couldn't really work, keep working. I was almost done with tennis. He brought this fire back and the motivation. He trusted that I still can play good tennis and he transferred this to me."

The 2018 French Open and 2019 Wimbledon champion added: "Physically I'm good. Mentally I'm good, so I think it's all positive."

Halep, who won the Canadian Open in 2018, has reached the semi-finals for the fifth time in her career where she will take on seventh seed Jessica Pegula.

Pegula got past Yulia Putintseva 6-3 6-3 in one hour and 21 minutes. Qualifying for the last four at the Canadian Open for the second straight year.

Brazilian Beatriz Haddad Maia maintained her Canadian Open run, having ousted Swiatek in the third round and local favourite Leylah Fernandez in the second, with a 2-6 6-3 6-3 victory over Tokyo Olympics gold medalist Belinda Bencic in two hours and 11 minutes.

Haddad Maia became the first Brazilian to reach the semi-finals of a WTA 1000 tournament. She will face Karolina Pliskova in the semi-finals after the Czech 14th seed beat Qinwen Zheng 4-6 6-4 6-4.

Serena Williams' decision to begin winding down her tennis career has saddened world number one Iga Swiatek and Belinda Bencic, who defeated the 40-year-old on Wednesday.

Williams announced on Tuesday that she is about to retire, saying "the countdown has begun" as she looks to "move in a different direction".

While the 23-time singles grand slam champion did not put a specific timeline on her remaining days in tennis, her comment about looking for new challenges after "these next few weeks" suggests the US Open – which she has already been included on the entry list for and starts at the end of August – will be her swansong.

That announcement came on the back of Williams' first singles win in 430 days, a defeat of Nuria Parrizas-Diaz at the Canadian Open in Toronto, but she was subsequently eliminated by Bencic on Wednesday, when the reality of her farewell tour set in.

Williams failed to hold back the tears as she said goodbye to the Toronto crowd for the last time as a player, and Bencic herself could not help feeling a little overcome

She said: "It was definitely very special. I think it was more than just the usual tennis match, also just really exciting, and also a little bit overwhelming for me, of course.

"[It's] great, I can be part of her career and her story and this was just really nice and I'm just really appreciative and honoured to play her so many times, and also here in Toronto.

"I mean, she's really the greatest of all time, so it's really exciting. I could have been on the court against her so many times and even today I really enjoyed it a lot. It was sometimes like a pinch me moment again."

Williams finished five different calendar years as the highest-ranked player in the world, a record only Steffi Graf and Martina Navratilova can better.

Swiatek, the current world number one, looks to be the best-placed of the next generation to challenge that achievement, though she recognises a degree of fortune in not having to face Williams at the peak of her powers.

"Well it's always pretty sad when you see such a career coming to an end, but on the other hand she's a legend and I feel like she's done so much," Swiatek added.

"It's really amazing. I'm pretty sad that I wasn't able to play against her and experience that her being the strongest one on tour, but on the other hand, I would be losing against her if I played [her at] that time, so that's fine!

"But she's a legend and everything that she has done on court and off court, she's basically a superstar and the way she handled playing tennis and business and also being a mother, it's mind-blowing. So I'm pretty sure that she's going to have a great second part of her career."

The Serena Williams' farewell tour in Toronto is over after she was knocked out of the Canadian Open 6-2 6-4 by 12th seed Belinda Bencic on Wednesday.

Williams, playing for the first time since declaring on Tuesday her intention to retire after this month's US Open, was no match for Tokyo Olympics gold medalist Bencic.

The 23-time major winner was unable to claim back-to-back WTA singles wins for the first time since last year's French Open, having defeated Nuria Parrizas-Diaz for her first victory in 430 days on Monday.

Bencic triumphed in one hour and 17 minutes, winning 84.2 per cent of first-serve points and converted five of eight break points throughout the match.

Williams' power was on show with 13 winners, but Bencic was physically more capable and decisively managed 25 winners with only 13 unforced errors.

Elsewhere, 2019 US Open winner and local hope Bianca Andreescu edged Alize Cornet in a see-sawing clash in the evening, winning 6-3 4-6 6-3 in two hours and 26 minutes.

Fourth seed Paula Badosa and fifth seed Ons Jabeur, who was last month's Wimbledon runner-up, were forced to retire due to injury.

Spanish 24-year-old Badosa withdrew against Yulia Putintseva 7-5 1-0 due to muscle cramping, while Zheng Qinwen had a walkover against Jabeur 6-1 2-1 due to abdominal pain.

Top seed Iga Swiatek brushed aside Ajla Tomljanovic 6-1 6-2 in 64 minutes. The win means Swiatek is the first player to win 15 WTA 1000 matches in straight sets in a row since 2009.

Canadian 13th seed Leylah Fernandez also bowed out, going down 7-6 (7-4) 6-1 to Brazil's Beatriz Haddad Maia, who will face Swiatek in the third round.

Second seed Anett Kontaveit lost 6-4 6-4 to Jil Teichmann in one hour and 27 minutes. Teichmann will next face Simona Halep who won in 71 minutes against Zhang Shuai 6-4 6-2.

Sixth seed Aryna Sabalenka got past Sara Sorribes Tormo 6-4 6-3 to set up a third-round meeting with Coco Gauff after she defeated Wimbledon champion Elena Rybakina 6-4 6-7 (8-10) 7-6 (7-3) in an epic that lasted two hours and 49 minutes.

Jessica Pegula won 6-2 7-5 over American qualifier Asia Muhammad to progress through to face Camila Giorgi after she knocked off Elise Mertens 7-3 7-5.

Third seed Maria Sakkari triumphed in three sets 6-2 4-6 6-2 over Sloane Stephens and will face Karolina Pliskova next after the Czech beat Amanda Anisimova 6-1 6-1.

Eighth seed Garbine Muguruza won 6-4 6-4 against Kaia Kanepi and Alison Riske toppled 16th seed Jelena Ostapenko 7-6 (7-2) 0-6 7-5.

The day after declaring her impending retirement, Serena Williams was full of emotion and admitted it had been a "pretty interesting 24 hours" for her.

Williams revealed on Tuesday in an article in Vogue that "the countdown has begun" for her retirement with this month's US Open set to be the 23-time major winner's last tournament.

The 40-year-old was knocked out of the Canadian Open on Wednesday by Belinda Bencic 6-2 6-4 and spoke after the match for the first time publicly since declaring her intention to retire.

"It was a lot of emotions obviously," Williams said during the on-court post-match interview.

"I've loved playing here [Toronto], I've always loved playing here. I wish I could have played better but Belinda played so well today.

"It's been a pretty interesting 24 hours."

Williams, who won the first of her 23 Grand Slam titles way back in 1999 at the US Open, was emotional about the reception from fans to her announcement.

"It's just been so memorable," Williams said.

"Like I said in my article, I'm terrible at goodbyes. But goodbye, Toronto."

Williams has already been named on the entry list for the US Open, which starts at Flushing Meadows at the end of August.

The former world number one had claimed her first WTA singles win in 430 days on Monday when she defeated Nuria Parrizas-Diaz in preparation for her US Open farewell.

Petra Martic beat home favourite Belinda Bencic to set up a semi-final against Caroline Garcia at the Ladies Open Lausanne.

Martic toppled the second seed with a 6-3 7-6 (7-2) victory on Friday.

The unseeded Croatian, who was beaten by eventual champion Elena Rybakina in the fourth round at Wimbledon last week, claimed the only break of the first set to lead 5-3 and held her nerve to serve it out. 

Bencic twice came from a break down in the second set to force a tie-break, but Martic raced into a 6-0 lead and duly moved into the last four.

The 31-year-old Split native will come up against Garcia, who beat Sara Sorribes Tormo 6-4 6-1.

Frenchwoman Garcia also reached the last 16 in the grass-court grand slam at SW19 and has won 11 of her past 12 matches.

Unseeded duo Olga Danilovic and Anastasia Potapova will contest the other semi-final following victories over Simona Waltert and Wimbledon quarter-finalist Jule Niemeier respectively.

At the Budapest Grand Prix, Anna Bondar is through to the last four without dropping a set in her homeland after defeating Martina Trevisan 6-4 6-1.

Ninth seed Bondar will face Bernarda Pera, who beat Elisabetta Cocciaretto 6-4 6-3. Yulia Putintseva had won all eight games before Lesia Tsurenko retired from their quarter-final due to injury and she will take on Aleksandra Krunic, who cruised past Wang Xiyu 6-0 6-1.

Top seed Danielle Collins suffered a shock defeat in a marathon first-round match with Simona Waltert at the Ladies Open Lausanne.

Collins, ranked a career-high seventh in the world, lost to a player 147 places below her as home hope Waltert prevailed in a final set tie-break.

The American battled back from a break down three times in the final set and had three match points in the tie-break.

But Collins could not find the telling blow as Waltert improbably turned the tide to win five successive points, and claim her first top-10 win 6-7 (5-7) 6-3 7-6 (8-6) after three hours and one minute of play.

Meanwhile, Waltert's compatriot Belinda Bencic survived a scare to avoid joining Collins on the casualty list, recovering from a set down to beat Diane Parry 3-6 6-3 6-1.

World number 77 Parry has claimed notable recent scalps in former French Open champion Barbora Krejcikova at Roland Garros and Kaia Kanepi at Wimbledon, but was denied another as the second seed hit back to advance. 

But there was no joy for fifth seed Nuria Parrizas-Diaz, who suffered defeat to Petra Martic, while eighth seed Varvara Gracheva lost to qualifier Eva Lys.

However, third seed Irina-Camelia Begu overcame Tamara Korpatsch in straight sets and sixth seed Caroline Garcia - fresh off a fourth-round run at Wimbledon - defeated Jasmine Paolini 6-3 6-3.

At the Hungarian Grand Prix, second seed Martina Trevisan came from a set down to survive against Natalia Szabanin and third seed Yulia Putintseva and ninth seed Anna Bondar also prevailed.

Ons Jabeur won the Berlin Open to seal her third career title following Belinda Bencic's retirement in the second set.

The win sees Jabeur rise to a career-high of number three in the world as the Tunisian – who was winning  6-3 2-1 when Bencic succumbed to an ankle injury – capitalised on her top seed position for the tournament.

With Jabeur on serve to clinch the first set, Bencic rolled her ankle and required treatment in a three-minute medical timeout – with Jabeur swiftly nosing herself ahead on the restart with an ace.

Olympic gold medallist Bencic pushed to continue but came to the net to retire when trailing 2-1 in the second set, taking Jabeur's tally of wins in 2022 to 30, a total that is only bettered by world number one Iga Swiatek.

Victory marked Jabeur's second title of 2022, with the 27-year-old having previously won the Madrid Open.

Jabeur had plenty of support from the crowd throughout the tournament, and said: "I cannot forget how amazing the crowd is, Tunisians are amazing, thank you for coming. I hope I can come back next year, it's been great to come back to Berlin."

Bencic paid tribute to her opponent following the game, saying: "You deserve this title, I really don't want to take this moment away from you because I think you played incredible tennis.

"This is the best tennis of your life, so I hope you continue. You gave me a really hard time, maybe it was one serve too much for me. This is your moment so I want you to enjoy it and focus on your title."

Jabeur continues her Wimbledon preparations at Eastbourne next week, competing in both the singles and doubles event – she will play alongside Serena Williams – while Bencic will be hoping to recover in time to feature in the season's third grand slam.