Donna Vekic produced a spectacular second set to shock world number seven Maria Sakkari 7-6 (7-3) 6-1 in the first round of the San Diego Open on Tuesday.

After a hard-fought first set where both women were able to convert one of their four break point opportunities, Vekic took control in the tie-breaker and carried that momentum in the second set.

Vekic won 65 per cent of her service points in the second set, while Sakkari could only muster a 47-per-cent success rate, despite having a significant edge in first-serve accuracy (79 per cent to Vekic's 53 per cent).

The Croatian only had two break point opportunities, and that is all she needed, taking both to run away with one of the biggest wins of her career.

Vekic will play Karolina Pliskova in the second round after the Czech defeated America's Caroline Dolehide 6-3 6-4.

Pliskova, ranked 22nd in the world, had no issue with the world number 181 in one of Tuesday's biggest mismatches, nabbing a break-to-love in the first set before taking a quick double-break to begin the second.

World number 11 Daria Kasatkina was too strong for Leylah Fernandez, cruising to a 6-2 6-2 victory in exactly one hour.

Sloane Stephens earned a shot against world number five Aryna Sabalenka in the second round after getting the better of Switzerland's Jil Teichmann 6-1 7-6 (7-2).

World number 13 Garbine Muguruza was clearly not at 100 per cent, retiring hurt after losing the first five games of her match against China's Qinweng Zheng, and Coco Gauff will resume her contest against Robin Montgomery leading 6-3 3-2 after rain halted the action for the day.

Anhelina Kalinina progressed to round two of the Transylvania Open after opponent Eugenie Bouchard retired injured in Cluj.

Ukrainian world number 45 Kalinina took the opening set 6-3 before a hip injury prevented Bouchard from continuing.

The Canadian revealed she had retired as a precaution having undergone an MRI on Monday, and did not wish to aggravate the issue any further.

"I'm just disappointed to have ended my tournament in Romania this way because I really loved being here in Cluj," she said. "I pulled my hip flexor a few days in practice. I tried everything to be ready for this match.

"I got an MRI yesterday, and didn't show anything too bad, so I thought I could play. But it was getting worse as the match went on. To avoid a big injury, I figured it would be best to retire.

"I absolutely hate retiring, I wish I could've done better here, but I hope to be back."

Fourth seed Anastasia Potapova beat Ann Li 6-2 7-6 (7-5) to set up a clash with Viktorija Golubic, who overcame Diane Parry in straight sets.

Seventh seed Xiyu Wang advanced in straight sets against home favourite Jaqueline Cristian, while Harriet Dart required just 64 minutes to wrap up a commanding 6-2 6-0 victory over Oceane Dodin.

In a first-round clash between two of the world's top-20, Danielle Collins eliminated Caroline Garcia 6-2 7-6 (7-4) from the San Diego Open on Monday.

Garcia, the world number 10, entered the contest off back-to-back losses for the first time since March, and Collins made it three in a row as she was just a little too good with both her serving and return game.

Collins won 63 per cent of her service points, with Garcia at 52 per cent, and she ended up securing five breaks in the match.

She will play Martina Trevisan in the second round after the Italian defeated Colombian qualifier Camila Osorio 6-3 6-4.

Neither player had an ace in the match, but the big differentiating factor was Trevisan's ability to win points off her second serve, converting 50 per cent of her chances while Osorio won only one of nine (11 per cent).

The only qualifier of the day to get a win was Louisa Chirico, who beat fellow American Alison Riske-Amritraj 1-6 7-5 7-6 (7-5).

Chirico, the world number 196, will be rewarded for her win with a showdown against world number four Paula Badosa.

Madison Keys had no issues dealing with Australian qualifier Ellen Perez 6-1 6-4 in just over an hour, and Coco Vandeweghe defeated Sofia Kenin 6-1 1-6 6-4.

In the last match of the night, Canada's Bianca Andreescu won a two-hour-and-40-minute battle against Russia's Liudmila Samsonova 7-6 (7-1) 4-6 6-2.

Seeds Ana Bogdan and Marta Kostyuk crashed out of the Transylvania Open in the first round.

Home hope Bogdan, seeded third in Cluj-Napoca, was beaten in straight sets by Jule Niemeier, who showed the quality that helped her reach the last eight of Wimbledon in a 7-6 (7-5) 6-2 win.

Ukrainian Kostyuk, meanwhile, lost in three sets to Jasmine Paolini.

The sixth seed took a tight first set but Paolini broke Kostyuk five times thereafter en route to a 5-7 6-3 6-4 triumph.

Eighth seed Anna Bondar enjoyed a better day, prevailing 6-4 6-2 over Elina Avanesyan, while there were also wins for Dayana Yastremska, Anna Blinkova and Ysaline Bonaventure.

Barbora Krejcikova completed a fairytale home tournament as she won the Ostrava Open by beating world number one Iga Swiatek 5-7 7-6 (7-4) 6-3 in Sunday's final.

Krejcikova lifted the Tallinn Open last week for her first title of the season, and made it two from two with an impressive run to the final before a hard-fought triumph over Swiatek to earn a ninth straight victory and another championship trophy.

Swiatek herself had won 10 matches on the bounce, and the Pole raced to five of the first six games to lead the opener 5-1, though Krejcikova rattled off four straight games to level it up. 

However, after making it 6-5, Swiatek then found a crucial break to clinch the first set.

The second went all the way to a tie-break, which Krejcikova took the ascendancy of by putting herself 6-1 up, and despite a late Swiatek rally, the Czech 26-year-old finally levelled the match after watching four set points come and go.

In the decider, neither could find a break until the eighth game, with Krejcikova doing so to put herself within a game of winning.

And in an extraordinary final stand, Swiatek survived five championship points before her resistance was ultimately broken to deny her an eighth final victory in 2022.

It was Krejcikova's first win against Swiatek, having lost their previous two meetings, as the seventh seed sealed an incredible victory.

Elise Mertens claimed her first WTA title of the year after defeating Alize Cornet in straight sets to capture the Jasmin Open crown on Sunday.

The world number 42 reeled off the last 11 games as she soared to a dominant 6-2 6-0 victory after just 80 minutes in Monastir.

Mertens landed the seventh WTA title of her career - and first since the 2021 Gippsland Trophy - following a timely return to form off the back of a disappointing 2022 that had seen her reach just two quarter-finals.

The Belgian overcame Cornet in three sets when they met in St. Petersburg earlier this year, and she quickly gained the upper hand in the fifth contest between the pair.

Mertens rescued two break points to hold for 2-2, before breaking twice as she eventually cruised to the opening set.

A late wildcard in Tunisia, Cornet had progressed to her first final since Chicago last year without dropping a set, and was targeting her first silverware since triumphing in Gstaad four years ago.

But the world number 37 could not establish any momentum in her quest to get back into the final; nine double-faults certainly hindering her intentions.

Mertens fully capitalised. The fifth seed won 83 per cent of her first-service points, while breaking a further three times as she breezed to a commanding victory.

World number one Iga Swiatek will face Barbora Krejcikova in the Ostrava Open final after beating Ekaterina Alexandrova on Saturday.

Swiatek continued her stellar season with a 7-6 (7-5) 2-6 6-4 victory over the Russian.

A tie-break was needed to settle the opening set, with Swiatek securing a crucial break of serve when 6-5 up.

The Pole was caught off guard in the second set as Alexandrova took it the distance, before Swiatek claimed the solitary break of the decider to lead 4-3 and did not allow her opponent a way back.

Swiatek, who has 60 wins to her name in 2022, will do battle with Krejcikova in the championship match after she came from a set down to defeat Wimbledon champion Elena Rybakina 3-6 7-6 (7-4) 6-4.

Rybakina served 17 aces to Krejciokva's two, but the Czech 26-year-old battled to victory to put herself in the final of her home tournament.

At the Jasmin Open, Alize Cornet knocked out second seed Veronika Kudermetova with a 6-4 6-3 triumph to clinch her place in Sunday's final.

Cornet saved nine of 11 break points to beat the world number 12 and has not dropped a set all week at the tournament in Tunisia.

Elise Mertens awaits Cornet in the final after a 6-4 6-0 success over Claire Liu, who knocked out top seed Ons Jabeur on Friday.

Mertens broke Liu at 5-4 up to take the first set before emphatically sealing victory with a sublime second in which she won 24 of the 29 points.

Home favourite Ons Jabeur was on the end of a big upset at the Jasmin Open on Friday as the world number two was eliminated by Claire Liu in the quarter-finals.

Jabeur saw off Ann Li and Evgeniya Rodina in straight sets to reach the last eight, but Liu – ranked 73 in the world – came out on top 6-3 4-6 6-4.

Liu is now into her second semi-final of the season and will face Elise Mertens, who defeated Moyuka Uchijima 6-0 3-6 6-4 in the final match of the day.

Second and third seeds Veronika Kudermetova and Alize Cornet will meet in the other semi after beating Diane Parry and Tamara Zidansek respectively in straight sets.

At the Ostrava Open, meanwhile, tournament favourite Iga Swiatek reached her 10th semi-final of the year with a 6-4 6-4 victory over qualifier Caty McNally.

Swiatek needed nearly two hours to seal her 59th victory of the season – just one short of tying Caroline Wozniacki, the most recent female to hit 60 wins in a calendar year (2017).

She will now face Ekaterina Alexandrova, who proved too strong for Tereza Martincova in a 6-1 4-6 6-1 victory.

Another grand slam winner in Barbora Krejcikova earlier beat Alycia Parks 7-6 (9-7) 6-3 on home soil to maintain her positive form, a week after triumphing at the Tallinn Open.

Awaiting her in the semi-finals is Elena Rybakina following the reigning Wimbledon champion's 7-6 (7-5) 6-4 victory against Petra Kvitova.

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.

Emma Raducanu has withdrawn from the Transylvania Open with a wrist injury, compounding a miserable 2022 for the British number one.

The teenager became an overnight star on the WTA Tour last year when she won the US Open women's singles title in her first appearance at Flushing Meadows.

However, her attempts to follow up that success have been hamstrung by a succession of niggles, with Raducanu currently down at 67th in the world rankings.

Her withdrawal from next week's event in Romania – the country from which her father hails – is just the latest injury problem, with Raducanu having been forced to quit during the semi-finals of last month's Korea Open with a glute problem.

This followed a first-round retirement at the Nottingham Open before Wimbledon, though Raducanu ultimately recovered to reach the second round of the grass-court major.

A first-round exit at the Ostrava Open this week, followed by the latest setback, means Raducanu's season appears effectively over, with the 19-year-old likely to set her focus on regaining full fitness ahead of 2023.

Iga Swiatek is through to the quarter-finals of the Ostrava Open after Ajla Tomljanovic retired hurt in their second-round match on Wednesday.

The world number one had won the first set 7-5, but her Australian opponent was forced to concede at 2-2 in the second.

Swiatek is now the female player with the most wins in a single year (58) in the last five seasons. Former world number one Ash Barty recorded 57 victories in 2019.

The second seed in Ostrava is out after Paula Badosa was beaten 7-6 (7-4) 6-4 by Petra Kvitova in front of a delighted Czech crowd, while Elena Rybakina is also through to the last eight after coming from behind to win against Aliaksandra Sasnovich 6-7 (5-7) 6-4 7-5.

Wednesday's two other matches saw more success for Czech participants as Karolina Muchova beat seventh seed Beatriz Haddad Maia 6-4 6-4, while Barbora Krejcikova defeated Shelby Rogers 6-2 6-2.

There was less Czech joy at the Jasmin Open in Tunisia, where Katerina Siniakova was beaten 7-5 6-2 by Claire Liu.

Elsewhere, number three seed Alize Cornet eased past Harriet Dart 6-3 6-4, Elise Mertens came from behind to beat Despina Papamichail and Diane Parry went through against French compatriot Lucrezia Stefanini after the latter retired hurt in the second set.

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.

Elena Rybakina advanced to the last 16 at the Ostrava Open on Monday, but fellow former grand slam winner Victoria Azarenka exited at the first hurdle.

Rybakina, who has struggled for consistency since victory at Wimbledon earlier this year, came back from a set down to dispatch Madison Keys with a 5-7 6-3 6-3 win.

She could face eighth seed Jelena Ostapenko in the next round, but one name not in the draw will be Azarenka, who could not claw back victory against Ekaterina Alexandrova in a 6-4 4-6 2-6 defeat.

Alexandrova is in line to play either Emma Raducanu or Daria Kasatkina in the next stage.

Meanwhile, top seeds Iga Swiatek and Paula Badosa earned the identity of their opponents after receiving first-round byes.

Swiatek will play Ajla Tomljanovic, who progressed in straight sets against Zhang Shuai, as Badosa faces Petra Kvitova, who was made to work a little harder in three by Bernarda Pera.

At the Jasmin Open, third, fifth and seventh seeds Alize Cornet, Elise Mertens and Katerina Siniakova each advanced with respective straight-sets routs of Laura Pigossi, Jaqueline Cristian and Chloe Paquet – the latter retiring as she trailed 4-0 in the second set.

But eighth seed Magda Linette is out after letting an early lead slip against Lucrezia Stefanini, who celebrated a 2-6 6-4 6-4 victory.

Iga Swiatek warned the tennis schedule is "not safe" and "could cause injury" as she pulled out of the Billie Jean King Cup Finals.

The world number one was due to represent Poland in an event that will be staged in Glasgow from November 8-13, but withdrew on Monday.

That competition will start just a day after the WTA Finals finish in Fort Worth, Texas.

US and French Open champion Swiatek criticised governing bodies the WTA and International Tennis Federation (ITF), who run the Billie Jean King Cup, over the calendar.

"I was thinking it through a lot and discussing it with my team, but I will not be able to play at the Billie Jean King Cup in Glasgow," Swiatek posted in an Instagram story.

"It makes me sad. I'm very sorry, because I play for Poland whenever it's possible and I always give it my best.

"Playing in Poland this year [in the qualifiers] was an honour and I hoped to do this again at the end of the season.

"I'm disappointed that tennis governing bodies didn't come to an agreement on something as basic as the calendar of tournaments, giving us only one day to travel through the globe and changing the time zone.

"The situation is not safe for our health and could cause injury."

Barbora Krejcikova claimed her first title of the year by beating top seed Anett Kontaveit in the inaugural Tallinn Open final on Sunday.

Krejcikova had not won a singles title since her third triumph of 2021 in Prague last July, but ended her drought with a 6-2 6-3 defeat of the top seed.

The Czech ended the home favourite's hopes of being crowned champion in a showpiece match that was over in an hour and 21 minutes.

Kontaveit had won 24 consecutive indoor matches on hard courts, but she was no match for the 2021 French Open champion.

Krejcikova won 71 per cent of points on Kontaveit's second serve, breaking twice in the opening set and three times in the second.

She drew first blood to go 4-2 in the first following precise groundstrokes off both wings, then broke for a second time to seal an opening set in which Kontaveit made 13 unforced errors.

World number four Kontaveit responded with a break in the opening game of the second set, but failed to back that up with a hold.

Kontaveit had the initiative again at 3-1, but there was a sense of deja vu as her opponent broke straight back and served out the match after moving 5-3 in front with another break.