Angelique Kerber and Maddison Keys each required three sets to reach the third round of the Indian Wells Open, while Coco Gauff held off Claire Liu to advance on Friday.

Number 15 seed Kerber was handed a banana skin tie of sorts against Zheng Qinwen and was made to work hard for her 6-2 5-7 6-4 victory against the rising Chinese star.

Zheng battled back with three breaks of serve in the second set to level up and led 4-1 in the decider, but her opponent dug deep to prevail in a time of two hours and 18 minutes.

Daria Kasatkina awaits Kerber – who had not previously won this calendar year – after the Russian beat Katie Volynets 6-4 4-6 7-5 earlier in the day.

Keys was also pushed all the way in her clash with Misaki Doi before coming out on top 6-4 3-6 6-1 to set up a meeting with Alison Riske in round three.

The Australian Open semi-finalist struggled in the second set after holding her serve throughout the first, though she had enough quality to see off her Japanese opponent.

Gauff had less trouble against fellow American Liu, advancing in a little over an hour to reach the third round, the stage in which she was eliminated on her debut here last year.

She will take on former world number one Simona Halep on Sunday, the day she turns 18, in a rematch of their last-16 showdown from Wimbledon three years ago.

Emma Raducanu and Iga Swiatek are among the others already through to the last 32 in California.

Elina Svitolina and Simona Halep both fell in the first round of the Qatar Ladies Open, while Garbine Muguruza and Anett Kontaveit eased through on Monday.

Former world number one Halep, champion in Qatar back in 2014, was off the pace as Caroline Garcia claimed just her second win in nine meetings against the Romanian with a 6-4 6-3 triumph.

Number 10 seed Svitolina also suffered an early exit after ending up on the wrong side of an almost three-hour slog, with Tereza Martincova eventually succeeding 6-7 (2-7) 7-5 7-6 (7-5).

But fifth favourite Muguruza – a two-time finalist, including in 2021 – did not have much as trouble as she outfought Sorana Cirstea 7-6 (7-4) 6-1 in a second-round contest, with Kontaveit coasting through to round three in similar fashion with a 6-2 6-3 win over Ana Konjuh. 

Jelena Ostapenko, who is a former finalist in Doha and champion in Dubai last week, managed a sixth consecutive victory in the Middle East as she downed Oceane Dodin 6-4 6-2 to reach the second round, while 11th seed Elena Rybakina fell at the first hurdle to Jacques Cristian in a 6-4 6-3 loss.

Angelique Kerber, the 13th ranked player at the tournament, was another surprise first-round loser as she fell 4-6 6-3 6-2 to Jil Teichmann.

Cori Gauff secured her spot in the second round with a straightforward 6-2 6-3 victory over American compatriot Shelby Rogers, while 16th seed Elise Mertens battled to a 6-3 2-6 7-5 win over Jasmine Paolini.

Meanwhile, defending champion Petra Kvitova had no trouble easing past Irina-Camelia Begu 6-3 6-1, and Daria Kasatkina edged out Ajla Tomljanovic 6-4 6-7 (4-7) 6-2.

Emma Raducanu has appointed Torben Beltz as her new coach almost seven weeks after parting company with Andrew Richardson.

The 18-year-old rose to international fame in September when she pulled off the incredible feat of clinching the US Open before ever even winning a single match on the WTA Tour.

Raducanu beat fellow teenager Leylah Fernandez to become the first qualifier in tennis history to win a grand slam and youngest winner of a women's major since 17-year-old Maria Sharapova took the Wimbledon title in 2004.

But she announced soon after that she and Richardson were no longer working together, with Raducanu continuing in the meantime without a coach as she scoured for someone with more WTA Tour experience.

Since the US Open, she has played just five matches and lost three of them, the latest coming on Tuesday as she suffered a 6-1 6-7 (0-7) 7-5 defeat to Wang Xinyu at the Linz Open, where Raducanu was the top seed.

But as she looks ahead to starting pre-season at the end of November, Raducanu will begin working with Beltz in the hope of building on her incredible breakthrough year.

The German was Angelique Kerber's coach during her US Open and Australian Open successes in 2016, and Raducanu is excited to get started.

Speaking after her defeat in Linz, Raducanu said: "You guys cracked it! It's obviously a great privilege to be working with such an experienced coach.

"I'm definitely very excited to work with him throughout the pre-season and into next year. I'm feeling excited about all the work that is to come.

"I think he brings a lot of experience. Obviously he's worked with Kerber, who's such a great player and has done extremely well, won three slams. I think that experience definitely helps with someone as inexperienced as me.

"He can help guide me through, which I feel really confident about, and also he's a really positive, cheerful guy who brings great energy to the team, so I think that's also important when you're travelling on the road for quite a long time on the tour."

Belinda Bencic fought back to beat Angelique Kerber in a blockbuster showdown and help Switzerland eliminate Germany on day two of the Billie Jean King Cup in Prague.

Germany lost to hosts Czech Republic on the opening day and were brushed aside 3-0 by Switzerland on Tuesday, with world number nine Kerber losing 5-7 6-2 6-2 to Bencic.

Kerber was carrying an injury and was outlasted by the Olympic gold medallist, with that triumph coming after Viktorija Golubic defeated Andrea Petkovic 6-4 7-5.

Golubic and Jil Teichmann added further gloss to the scoreline by overcoming Anna-Lena Friedsam and Nastasja Mariana Schunk in the doubles.

Switzerland will now meet the Czech Republic in a winners-takes-all contest to determine who finishes top of Group D.

The upset of the day came in Group B as Australia beat Belgium 2-1, with Daria Gavrilova kicking things off by beating Greet Minnen 6-4 1-6 6-4.

Storm Sanders then battled back to beat Elise Mertens 4-6 7-6 (7-5) 6-0, rendering Mertens and Minnen's doubles win nothing more than a consolation. 

In Group A, Russia cruised to a 3-0 win over Canada.

Daria Kasatkina beat Carol Zhao 6-3 6-1 and Anastasia Pavlyuchenkova was too strong for Rebecca Marino as she prevailed in three sets.

Slovakia top Group C, meanwhile, after beating the United States 2-1. Shelby Rogers fell 6-4 6-4 to Viktoria Kuzmova before Danielle Collins levelled with a 6-3 6-2 win against Anna Karolina Schmiedlova.

That set up a decider in the doubles, which went the distance as the Slovakian pair of Kuzmova and Tereza Mihalikova prevailed 6-2 6-7 (5-7) 12-10 in a thriller with Caroline Dolehide and CoCo Vandeweghe.

Angelique Kerber was knocked out in the Californian desert after a straight-sets quarter-final defeat to Paula Badosa at the WTA Indian Wells Open.

Badosa, who made this year's French Open quarter-finals, squandered two match points at 5-2 in the second set against three-time grand slam champion Kerber before steadying to secure her fifth final-four appearance of the season on Thursday.

In the semi-finals, Badosa will face Tunisian 12th seed Ons Jabeur, who got past Anna Kontaveit in straight sets, confirming her historic rise into the top 10 of the rankings, as the first-ever Arab player to achieve the singles feat on either the WTA or ATP Tour.

KERBER TOPPLED BY BADOSA

Former world number one and 10th seed Kerber bowed out at Indian Wells, with Badosa triumphing 6-4 7-5 in 86 minutes.

In her Indian Wells debut, 21st seed Badosa responded strongly after fluffing two match points to become the first Spanish woman to make the event's semi-finals in 18 years.

"It sounds amazing," Badosa said during her on-court interview. "The second set was very mental. I wanted this match so badly. I got super nervous.

"For one second I thought who was on the other side of the net and I got more nervous against a three-time grand slam champion. It means a lot to me. It's amazing."

In the first set, Badosa broke Kerber at 4-4 before serving out the opening set where she was excellent on her first serve, staving off the German's only two break points.

The Spaniard raced to a 5-2 lead in the second set and had two match points on Kerber's serve. The experienced Kerber responded by holding serve and then breaking back, before levelling at 5-5.

But Badosa showed her mettle by winning the final two games, breaking Kerber for victory as she upped her level.

JABEUR SEALS TOP-10 BERTH WITH TRIUMPH

Jabeur defeated Estonian 18th seed Kontaveit 7-5 6-3 to move into the top 10 for the first time in her career.

The Tunisian will become the first Arab player to make the top 10 when the updated WTA rankings are made official on Monday, but she also qualified for the biggest semi-final of her career to date.

"It feels amazing," Jabeur said. "We've been working hard since years. When I spoke at the end of last season, I said I wanted to be in the top 10. People doubted us as a team, we proved them wrong.

"Being a top 10 means a lot but we're not going to stop here. We're going to go further hopefully."

Jabeur, who made this year's Wimbledon quarter-finals, triumphed in 86 minutes, although she did not have it all her way, in a match full of momentum swings.

The 27-year-old Jabeur had been a double break up at 4-1 in the first set before Kontaveit hit back to level at 5-5, only for her to break back immediately and serve out the set.

Jabeur broke Kontaveit to love at 3-3, rattling off the final three games, including two breaks, to secure victory and keep alive her hopes of making the WTA Finals.

Iga Swiatek was knocked out of the Indian Wells Open in the round of 16, the second seed headlining the list of casualties on Tuesday.

Swiatek was swept aside by Jelena Ostapenko in the battle between two previous French Open champions in the desert.

Elina Svitolina, reigning Roland Garros champion Barbora Krejcikova and US Open runner-up Leylah Fernandez were also sent packing from the WTA Premier 1000 event.

SWIATEK CRUMBLES

After top seed Karolina Pliskova was eliminated on Monday, 2020 French Open champion Swiatek crashed out following a 6-4 6-3 defeat to Ostapenko.

Ostapenko – the 2017 Roland Garros winner – rallied from a break down in each set to reach the quarter-finals at Indian Wells, where the 24th seed hit 25 winners to 21 unforced errors in 93 minutes.

"I knew it was going to be a very tough match because she's such a great player, she won a grand slam and she's playing great tennis," Ostapenko said.

Standing in the way of Ostapenko and the semi-finals is Shelby Rodgers, who edged Flushing Meadows finalist Fernandez 2-6 6-1 7-6 (7-4).

SVITOLINA UPSTAGED BY PEGULA

Svitolina's campaign in the desert did not go according to plan, the fourth seed crushed 6-1 6-1 by Jessica Pegula.

Pegula – the 2021 Australian Open quarter-finalist – dismantled Svitolina in just 68 minutes for her seventh last-eight appearance of the season and fourth at WTA 1000 level.

"I think I've just been making a lot of really good decisions in the right moments," said Pegula, who will face two-time grand slam champion Victoria Azarenka following her seventh top-10 victory. "That obviously comes with playing a lot of matches, winning and getting confidence... it's just been more belief that I can play at this level. I think this year, I realised that, and I've been having good results."

KERBER POWERS THROUGH AS KREJCIKOVA FALLS

Three-time major winner and 10th seed Kerber will feature in the quarter-finals after overpowering Ajla Tomljanovic 6-4 6-1.

Kerber will next meet 21st seed Paula Badosa, who shocked third seed and reigning French Open champion Krejcikova 6-1 7-5.

"I think I played a pretty good match today," Badosa said. "I knew I had to play on a high level against Barbora. She's an amazing player, very talented. We played before so I knew what I was going to find there on court. I'm feeling good and I'm very happy that I could play my best today."

Top seed Karolina Pliskova suffered a shock defeat while defending champion Bianca Andreescu and Coco Gauff also were on the wrong end of upsets Monday at the Indian Wells Open. 

World number 115 Beatriz Haddad Maia of Brazil stunned Pliskova in straight sets to reach the round of 16 at a WTA Premier 1000 event for the first time.

The 15th and 16th seeds, Gauff and Andreescu, also exited in two sets, albeit to seeded players. 

LUCKY LOSER OUSTS PLISKOVA 

Haddad Maia lost in the final round of qualifying but made the main draw as a lucky loser when Nadia Podoroska withdrew through injury, and she has made the most of that reprieve with a 6-3 7-5 defeat of the world number three. 

She had faced Pliskova once before and it did not go well, a 6-1 6-1 rout at the 2018 Australian Open, but the Czech struggled to find her trademark serve amid powerful winds in the California desert.

Pliskova suffered 12 double faults and won just 43.4 per cent of points on her serve, whole Haddad Maia saved nine of the 14 break points she faced on her own serve. 

KONTAVEIT STAYS HOT TO DETHRONE ANDREESCU

Haddad Maia next faces 18th seed Annett Kontaveit, who ousted Andreescu 7-6 (7-5) 6-3 to end the Canadian's dreams of a repeat. 

Kontaveit has won 15 of her last 16 matches, winning titles in Cleveland and Ostrava during that stretch. Monday, she captured the first set on her fifth set point before rallying from a 3-1 deficit in the second to run the table and seal the win.

"It was extremely close throughout the match and I was just trying to stay tough. I was ready for a tough match," Kontaveit said. "She's such a good player, such a great competitor, so I knew it wasn't going to be over until it was really over."

BADOSA BOUNCES GAUFF

Paula Badosa, the 21st seed, breezed past Gauff 6-2 6-2 as the American teen also had trouble with her serve, hitting just two aces after recording 12 in her previous match. 

In a meeting of the last two defeated finalists in the tournament, 10th seed Angelique Kerber beat 20th seed Daria Kasatkina 6-2 1-6 6-4. 

Third seed Barbora Krejcikova handled Amanda Anisimova with ease, 6-2 6-3. 

Ons Jabeur, the 12th seed, had little trouble in downing 22nd seed Danielle Collins 6-1 6-3. 

Garbine Muguruza could not keep the momentum going at the Indian Wells Open after winning a WTA title last week and the former world number one was followed out the door by Maria Sakkari.

Muguruza, who claimed the Chicago Fall Tennis Classic, was surprisingly upstaged 6-3 1-6 6-3 by Australia's Ajla Tomljanovic in an upset on Saturday.

Tomljanovic had been 0-6 against top-10 players this year heading into the match but had just enough to edge the fifth seed and two-time grand slam champion with some timely breaks of serve. 

The world number 47 Tomljanovic is into the third round at Indian Wells for the first time in seven appearances and next faces 26th seed Tamara Zidansek. 

"I was really looking forward to playing Garbine, because I did lose [to her] the last couple of times," Tomljanovic said in her on-court interview. "I did try to focus on that one time I beat her [in 2014], and tried to channel that energy, so I was really happy that I got through today."

GOLUBIC STUNS SAKKARI

Sixth seed Sakkari – a semi-finalist at this year's French and US Opens – also fell victim to a shock result, going out 5-7 6-3 6-2 to Viktorija Golubic in their first meeting. 

The pair kept trading service breaks in the opening set, five in all, before Golubic tightened up her game for the final two sets. 

After breaking the Swiss three times in the first set, Sakkari converted just one of four break points the rest of the match. 

Golubic had lost in the first round in her previous two trips to Indian Wells but is now on to the third, where she will face Anna Kalinskaya.

ANDREESCU HOLDS OFF RISKE

Former US Open champion Bianca Andreescu saw a potential straight-sets win slip away before recovering to defeat Alison Riske 7-6 (7-2) 5-7 6-2.

Andreescu – the defending champion after the 2020 WTA Premier 1000 event was cancelled due to the coronavirus pandemic – led 4-1 in the second set but watched her advantage evaporate as Riske forced a decider, which the Canadian ended up taking comfortably as she faced only one break point in the last. 

Top seed Karolina Pliskova eased past Magdalena Frech 7-5 6-2, while third-seeded Barbora Krejcikova was pushed to a third set before prevailing 6-4 3-6 6-1 against Zarina Diyas. 

Angelique Kerber – the 10th seed and three-time major winner – went the distance to beat Katerina Siniakova 6-1 6-7 (4-7) 7-5, while 15th seed Coco Gauff downed Caroline Garcia 6-3 6-7 (2-7) 6-1 in her debut match at the tournament. 

Ons Jabeur, the 12th seed, prevailed 6-2 6-7 (5-7) 6-3 over Anastasija Sevastova and 18th seed Anett Kontaveit – Andreescu's next opponent – moved on when Martina Trevisan retired down 6-3 5-2. 

Former world number one Angelique Kerber was stunned by Jil Teichmann as she lost 6-2 6-3 in Tuesday's Ostrava Open first-round tie.

World number 42 Teichmann raced to a memorable victory against the three-time grand slam winner in just over an hour as the left-hand collected her sixth win against a top-20 player this season.

Half of those wins have come this year as well, with the Swiss beating Naomi Osaka, Belinda Bencic and Karolina Pliskova in a breakthrough Cincinnati campaign.

Fifth seed Anastasia Pavlyuchenkova cruised through after negotiating a difficult first set against Ana Konjuh to win 7-6 (7-3) 6-1 in just over an hour-and-a-half.

Tereza Martincova's victory over fellow Czech Katerina Siniakova did not come as easily, though, with the former edging to a 5-7 6-4 7-6 (9-7) win in more than a three-hour slog.

Martincova, who is ranked 61st in the world, miraculously recovered from 5-0 down in the tie-break to save a match point before securing her first main-draw win in Croatia.

Yulia Putintseva experienced similar difficulties against Shuai Zhang, as she also battled out in a three-hour marathon and saved a match point to eventually succeed 5-7 7-6 (9-7) 6-4.

Canadian sensation Leylah Fernandez said she is pinching herself after continuing her fairytale run with a shock last-16 win over Angelique Kerber at the US Open.

After stunning defending champion Naomi Osaka in a third-round boilover at Flushing Meadows, giant-slaying teenager Fernandez conquered three-time grand slam winner Kerber 4-6 7-6 (7-5) 6-2 en route to the quarter-finals.

Kerber – the 2018 US Open champion – won the opening set in New York, however 18-year-old Fernandez staged a remarkable comeback on the eve of her 19th birthday to reach her first slam quarter-final.

"I did have to pinch myself a little bit to see that it actually happened, but like I said, I knew that my tennis, my level of tennis is there," Fernandez said post-match. "It's just a moment of time, opportunity, and I'm glad that I was able to get this opportunity now and that I was able to showcase what I can do in front of these players.

"Even if I would have lost, I would have been proud of myself with the way that I played, the way that I fought. I was lucky enough to get the win today and just getting this experience.

"It's my first fourth-round quarterfinals in a grand slam. I'm just going to enjoy it at 100 per cent, and tomorrow is going to be a new day."

Fernandez, who hit 45 winners to 34 unforced errors – added: "The match was incredible. I was playing well in the first set.

"Unfortunately I did a few mistakes. Her, as a great player, great champion, she noticed and she took advantage of it. I was able to refocus and fight back for the second.

"In the third, I was just enjoying every moment of it. Honestly, the crowd has been amazing, so thanks to them I was able to win."

"I'm just super happy," she continued. "I'm going to enjoy tonight as much as I can, and then once I'm off to bed, I'll try to forget about it so that I can get ready for tomorrow."

Sloane Stephens has detailed the online abuse she received after exiting the US Open to Angelique Kerber.

Stephens, who won at Flushing Meadows in 2017, was beaten 5-7 6-2 6-3 in the third round on Friday by three-time major champion Kerber.

The American had defeated outstanding teenager Coco Gauff in her previous match but could not maintain a title challenge in New York.

It was a defeat that prompted a shocking response on social media, Stephens revealed on Saturday.

"I am human," she wrote on her Instagram story. "After last night's match I got [more than 2,000] messages of abuse/anger from people upset by yesterday's result.

"It's so hard to read messages like these, but I'll post a few so you guys can see what it's like after a loss..."

Stephens then shared screenshots of a series of threatening, racist and misogynistic messages aimed in her direction.

She added: "This type of hate is so exhausting and never ending. This isn't talked about enough, but it really freaking sucks...

"I'm happy to have people in my corner who support me. I'm choosing positive vibes over negative ones.

"I choose to show you guys happiness on here, but it's not always smiles and roses."

World number one Ash Barty reached yet another final on Saturday at the Western and Southern Open, where she will face wildcard Jil Teichmann.

Barty is through to her sixth title match of the season – and first in Cincinnati – after beating Angelique Kerber in straight sets.

In action on the WTA Tour for the first time since winning at Wimbledon, having gone to the Tokyo Olympics in the intervening period, the Australian came through a sloppy spell in the second set to advance 6-2 7-5.

Teichmann is next, taking on Barty for the first time after a stunning run continued with victory over Karolina Pliskova.

The world number 76 had already eliminated Naomi Osaka and Belinda Bencic and was a deserving 6-2 6-4 winner against Pliskova.

Barty finds the balance

Barty had been racing towards victory when she took the opener on Kerber's serve, her second break, and then went 2-0 up in the second.

But Kerber gave the favourite a scare by winning each of the next three games, belatedly finding joy against the Barty serve.

The All England Club champion has won more matches than any other player on tour this year, though, and regained her composure to break twice more for a 39th triumph of 2021.

"It's never, ever a walk in the park against Angie," Barty said. "She's an exceptional competitor and I think early on in that second set she went to another gear and it took me a few games to go with her.

"That was the change – she was able to lift her game and, even though there were some close games, she won the big points early on in the second set.

"I'm glad that I was able to find a way through there in the end.

"I had to find the balance of being aggressive and not getting too passive and letting Angie dictate.

"She moves exceptionally well, puts the balls in difficult positions, and I felt like when I was able to control the court I did a better job.

"In the games I got broken, she just saw too many second serves and was able to be assertive.

"I'm really happy to get through in the end, and to be playing for a title here in Cincinnati is awesome."

'Random' run wears on

Despite facing three seeds in succession, Teichmann has not dropped a set since losing the first against Osaka in the last 16.

Continuing that sequence against Barty will be a tough ask, but few would have anticipated Pliskova being brushed aside quite so easily.

Teichmann herself has no explanation for a sensational run of form.

"It's tough to explain," she said. "When I ask my coaches what they think of me, they always say, 'You're just an unexpected person, you do random things', so I guess that's one of them.

"I'm feeling really, really good here, the conditions, serving good, moving well, when I can I attack, I defend... What I'm feeling here, I cannot even describe it.

"It's a dream. I'm playing centre court, a final against the world number one. I cannot ask for anything else."

Ash Barty reached her sixth semi-final of the year after winning the battle of grand slam champions against Barbora Krejcikova at the Western & Southern Open.

World number one and top seed Barty – the Wimbledon titleholder – dispatched French Open champion Krejcikova in straight sets in Cincinnati on Friday.

Another slam champion awaits Barty in the form of Angelique Kerber, while wildcard Jil Teichmann continued her fairytale run with victory over Olympic gold medallist Belinda Bencic.

Coffee the tonic for in-form Barty

Australian star Barty was too good for Krejcikova, winning 6-2 6-4 at the WTA 1000 tournament.

Barty had to battle from a break down in the second set against the fast-rising Krejcikova, who has shot up from 65th in the world to a career high of number 10 this year.

After extending her season record to 38-7, Barty talked about the importance of drinking coffee in the morning.

"I travel with a French press and an AeroPress, just to have two options. Usually every tournament we go to, one of us has a cafe that we have been to before, so I have got a little section of all my local cafes from the tournaments, so we try and get out to those if we can," she said.

"This year, some places we haven't been able to; some places we have. It's been nice to get some sort of a mixture, but I'm pretty simple. I'm just a black coffee cup in the morning, and then I'm set."

Three-time major champion Kerber is next up after she was 6-4 3-3 ahead before Petra Kvitova retired hurt due to a stomach problem.

Teichmann takes down another star

Unheralded Swiss and world number 76 Teichmann claimed another scalp, this time upstaging countrywoman Bencic 6-3 6-2 in the quarter-finals.

Teichmann stunned world number two Naomi Osaka en route to the quarters and maintained her giant-slaying form in Cincinnati, where 10th seed Bencic became the latest victim.

"We hugged before the match; we hugged after the match," Teichmann said of the Bencic meeting. "We know that once we step on court it's business, it's just another player I have to deal with, and she had the same mindset. At the beginning it's obviously a bit special, but once we're in it, we just look at the game, not looking at the opponent, or at least I do that way."

Teichmann will take on fifth seed Karolina Pliskova, who advanced to her second successive WTA 1000 semi-final after Paula Badosa retired down 7-5 2-0.

Ash Barty and Angelique Kerber set up a blockbuster Western and Southern Open semi-final – but Petra Kvitova suffered a fitness scare ahead of the US Open.

World number one Barty won 6-2 6-4 against French Open champion Barbora Krejcikova, who she also defeated in the fourth round during her Wimbledon title run last month.

Kerber and Kvitova then battled it out for the right to tackle Barty in the last four, but a quarter-final that was building momentum ended prematurely when two-time Wimbledon winner Kvitova found a recent stomach problem too troublesome.

Kerber was 6-4 3-3 ahead in the contest, having recovered from being an early break down in the second set, getting her game together as 31-year-old Kvitova began to suffer.

During an injury timeout, which Kvitova called after the fifth game of the second set, the Czech received a massage to her abdominal region and played on briefly, before walking up to the net to concede the match.

It remains to be seen whether the setback in Cincinnati might have consequences for her involvement at Flushing Meadows, with the US Open due to begin on August 30.

Kvitova wrote on Twitter minutes after coming off court: "I stayed out there as long as I could. I have been struggling with a stomach issue for several days and unfortunately couldn't finish the match today. Good luck Angie - sorry to end it that way - and can't wait for the next battle with you."

Kerber said in an on-court interview: "Of course, this is not the way you would want to win the match. I hope Petra will recover as fast as possible and be ready for the US Open.

"I know she's a big fighter and fights until the last points, so I hope she is not too bad and hope she is fine really, really soon."

Kerber has now won 14 of her last 15 matches, with the exception being her Wimbledon semi-final defeat to Barty.

Barty got through in a more routine manner on Friday, albeit having to battle from a break down in the second set against the fast-rising Krejcikova, who has shot up from 65th in the world to a career high of number 10 this year.

Barty said: "Barbora served exceptionally well early in that second set and was able to take advantage of a service game of mine where I just hit too many second serves.

"I wanted to try and get a little bit more positive on her service games and then try to get myself in the points a little bit more. I'm happy to run away with that one in the end."