Serena Williams has withdrawn from the US Open after failing to fully recover from a torn hamstring.

The 23-time grand slam champion, who won six of those titles at Flushing Meadows, has not played on the WTA Tour since sustaining the injury at Wimbledon in June.

She skipped last week's Western and Southern Open in the hope of being ready in time for the her home major in New York, but has now taken the decision to pull out of the event.

"After careful consideration and following the advice of my doctors and medical team, I have decided to withdraw from the US Open to allow my body to heal completely from a torn hamstring," Williams posted on her Instagram account on Wednesday.

"New York is one of the most exciting cities in the world and one of my favourite places to play – I'll miss seeing the fans but will be cheering everyone on from afar. Thank you for your continued support and love. I’ll see you soon."

Three-time Grand Slam winner Andy Murray has bemoaned his inconsistency within matches after bowing out of the Winston-Salem Open in the second round to Frances Tiafoe on Tuesday.

The 13th seeded American triumphed in one hour and 49 minutes over the Scot, who entered the event as a wildcard and had beaten lucky loser Noah Rubin in the first round.

Tiafoe won 7-6 (7-4) 6-3, saving three set points in the first set, before winning the tiebreak and taking command in the second.

Murray sent down 10 aces across the match but struggled on his second serve and on return.

"The positive thing is that I moved well and served well but my level is up and down with no real consistency," Murray said after the match in North Carolina.

"There are moments in matches where I play well and then I make mistakes or miss returns. I wish I wasn't doing that.

"My level is around 50 or 60 in the world. It's frustrating because if wasn't moving great and not feeling good physically then I would be a bit easier on myself. But when I'm winning a low percentage of second-serve points, that's got nothing to do with the physical side of things."

Sixth seed Marin Cilic also bowed out, losing 4-6 7-5 6-4 to Belarussian Ilya Ivashka, who sent down 16-13 aces.

Fifth seed Alexander Bublik was also bundled out, going down 6-2 7-6 (7-5) to Finland's Emil Ruusuvuori.

Top seed Pablo Carreno Busta dropped a set but edged past Kwon Soon-Woo 6-3 3-6 6-4.

British third seed Dan Evans came from behind to beat Lucas Pouille, while fourth seed Marton Fucsovics won in straight sets over Yosuke Watanuki.

Lucas Pouille continues to build momentum at the Winston-Salem Open after overcoming veteran Feliciano Lopez in straight sets.

Pouille was on the brink of elimination in qualifying after facing match point before booking his spot in the main draw.

Now, the Frenchman is preparing for the second round following his 6-1 6-4 victory over Lopez on Monday.

Pouille saved all four break points he faced as the former world number 10 claimed his first ATP Tour-level victory since April's Monte Carlo Masters.

Awaiting Pouille in the second round is third seed Daniel Evans, who received a bye in the opening round.

As for 14th seed Richard Gasquet, he prevailed 7-6 (7-4) 7-6 (8-6) against Egor Gerasimov at the ATP 250 event.

Elsewhere, Federico Coria and Jordan Thompson were among the players to progress.

Andy Murray was left in "the strangest situation" he has experienced before a tour match at the Winston-Salem Open following Nick Kyrgios' withdrawal.

Murray had been due to face Kyrgios in an enticing first-round clash in North Carolina, only for the Australian to pull out due to a knee issue.

Former world number one Murray was then drawn against a lucky loser from qualifying, which had only been completed shortly before Murray was due to go on court on Sunday.

The tight turnaround prompted Pierre-Hugues Herbert and Max Purcell to decline the chance to take on Murray, while another option, Yosuke Watanuki, ended up with a direct path to the main draw.

Home hope Noah Rubin, who played his college tennis at the same venue having competed for Wake Forest University, stepped in shortly after his qualifying defeat to Lucas Pouille.

Despite Rubin's best efforts, the challenge proved too much for him as Murray swept to a 6-2 6-0 win, capping a bizarre evening for the three-time grand slam champion.

"It is, by far, the strangest situation I've ever been in before a match on tour," said Murray. "It's pretty rare that you experience something new when you're 17 years into your career.

"I sort of knew at 6:15 that Nick wasn't going to play, but the qualifying was still going on. I was told that if I played a lucky loser, I would play this evening, but if I played against a qualifier the match would be suspended until tomorrow [Monday].

"Then I was told that I drew a lucky loser and I was going to be playing this evening against Pierre-Hugues Herbert, that was like 15-20 minutes after the last qualifying match finished, then Herbert decided he didn't want to play.

"Then they went down the list and none of them, Purcell and Watanuki, they didn't want to play either. And Rubin, who had obviously just finished playing 20 minutes beforehand said, 'yeah I'll do it. I'll play'.

"I kind of had like three opponents in the space of 45 minutes, I was warming up for the match to start at seven and then stopped and then prepared to play Herbert then he didn't want to play then Noah obviously decided but he'd just finished so it was a break and it was just very, very odd sort of 45 minutes, an hour before we went on."

Murray is due to face 13th seed Frances Tiafoe in the second round.

Alexander Zverev believes world number one Novak Djokovic remains the favourite for the upcoming U.S. Open despite the German backing up his Olympic gold medal with victory in Cincinnati.

The German world number four defeated Andrey Rublev in straight sets on Sunday to win the Western and Southern Open, claiming his fourth title of the ATP season.

The 2021 U.S. Open begins next Monday with Dominic Thiem, who defeated Zverev in the 2020 final, withdrawing from the men's draw along with superstar Roger Federer and Rafael Nadal.

Their absences have opened up an opportunity for the in-form Zverev to have a run at the title but the German insisted Djokovic, who he defeated in the Olympic semi-finals, is the player to beat.

"I do think that he's still the favourite," Zverev told reporters after his win in Cincinnati.

"I do think he's going to be playing incredible tennis there. He's going to be fresh, and I think there is also other guys that are in very good form. I think Rublev is in very good form, [Daniil] Medvedev, [Stefanos] Tsitsipas, all those guys are playing great tennis.

"It's definitely going to be an interesting US Open. But I'm also looking forward to it, because I know where I stand, I know how I'm playing, and I hope I can continue the work and hopefully play even better in New York."

Djokovic has not played since Tokyo 2020, where he lost his bronze medal match to Pablo Carreno Busta after his semi-final defeat to Zverev.

The Serbian world number one opted to withdraw from the mixed doubles' semi-final afterwards, citing a left shoulder injury.

"I think Novak will be back. He's obviously going to be the favourite but I think other guys are going to be in great shape,” Zverev said.

"I'm looking forward to the week. Let's see how it goes. But there is still one week to go. I still have a lot of work ahead of me. I have to find my rhythm in New York, as well."

Zverev, who had never won a match in Cincinnati prior to this year's event, has not lost a match since his Wimbledon fourth-round exit to Felix Auger-Aliassime in July.

World number one Ash Barty says her Western and Southern Open title holds her in "good stead" ahead of the U.S. Open which starts at Flushing Meadows next Monday.

The Australian defeated unheralded Swiss Jil Teichmann in straight sets in Sunday's final in Cincinnati in the perfect preparation for the U.S. Open.

Barty has never gone further than the fourth round at Flushing Meadows and did not compete in last year's U.S. Open due to COVID-19 concerns.

The 2021 Wimbledon champion, who also won the 2019 French Open crown, looms as a strong favourite for the women's singles title although she is typically refusing to get carried away.

"I think we're just excited that we've got matches under our belt in tough conditions here in Cincy, and that's put us in really good stead going into New York," Barty said.

"This week it was completely 'non-result-focused'. It was about preparing in the best way possible, knowing that we wanted to be ready for New York in a couple of weeks' time.

"Now that we've only got a week in between, we have played plenty of matches, and now it's about kind of refining as best we can to hopefully be feeling good come the first round in New York and just try and do the best that we can there."

On her favouritism, she added: "There are no certainties in sport, no certainties in tennis. It's just about playing each and every day as best you can as they come, and not focusing or concerning yourself or your self-worth with results."

Riding the wave of her Wimbledon triumph, Barty crashed out of the women's singles in the first round at Tokyo 2020 to Spaniard Sara Sorribes Tormo last month.

The Australian remained grounded after her Cincinnati victory and insisted preparations for the U.S. Open would stay normal.

"I think sometimes after big wins - and I felt it both times after the French Open and after Wimbledon - there's been a little bit of a big crash, more emotionally than anything else, because there's so much invested into that event," Barty said.

She added: "Our practice weeks before grand slams are quite normal. There is nothing fancy, no extra emphasis on anything.

"It's just gauged by how I'm feeling physically, how I'm feeling mentally, and we have had a lot of practice now as a team in being able to read each other and what we think is required.

"Then it's about going out there for the first round, whether it's the Monday or Tuesday, and try to do the best that I can. That's all I can ask of myself."

The draw for the U.S. Open will be revealed on Friday with Barty going in as the top women's seed, with Aryna Sabalenka second seed and reigning champion Naomi Osaka third.

Alexander Zverev claimed his fourth title of 2021 with a 6-2 6-3 victory over Andrey Rublev to win the Western and Southern Open.

The Olympic champion had not won a match in Cincinnati prior to this year's tournament, but Sunday's one-sided final capped a remarkable turnaround for the world number five.

Zverev raced into a 4-0 lead before securing the opening set 6-2 as he produced no errors across the first seven games.

The third seed carried on his domination, breaking Rublev in his opening service game of the second set to pave the way for the 17th ATP title of his career within an hour in the showpiece.

After paying tribute to "his best friend on Tour" Rublev, Zverev added in his on-court interview: "It is incredible that tennis can be back, sport can be back, and we can watch and play this beautiful sport again.

"I normally do not look forward to this week - not winning a single match in seven years - but this has now become one of my favourite times of the year for me, hopefully it can be for the next 10 to 15 years."

The 24-year-old reached the final of the US Open last year, though he will now eye going one step further as the tournament commences at the end of August.

Ash Barty won her first Western and Southern Open title on Sunday with a straight-sets defeat of Jil Teichmann in Cincinnati.

The world number one took her tally to 40 match wins and five WTA Tour titles in 2021 with a 6-3 6-1 victory.

Teichmann, ranked 76th in the world, had won all four of her meetings with top-10 players this season and accounted for Naomi Osaka, Karolina Pliskova and Olympic gold medallist Belinda Bencic during this exceptional week.

Beating Barty, however, proved a step too far. The Australian recovered from some early jitters, winning 85 per cent of points behind her first serve and breaking her opponent five times.

Teichmann's resistance faltered as errors saw her fall 5-3 behind in the opener and Barty won eight straight games to take command of the contest.

Barty needed just one match point to see out the victory, the first at Cincinnati by an Australian woman since Evonne Goolagong Cawley in 1973.

"I think being able to come through and play a really clean week and walk away with the title is probably not what I really expected of myself, but [it is] certainly nice," Barty, who did not drop a set all week, told the Tennis Channel.

Barty will be the firm favourite to win the US Open, where she has never before gone beyond the fourth round. The Flushing Meadows grand slam begins on Monday, August 30.

Rafael Nadal was "practically lame" before he called an early end to his season and has been "stumbling all year round", coach Carlos Moya has revealed.

Former world number one and 20-time grand slam winner Nadal will miss the upcoming US Open but hopes to return in 2022, yet Moya says there are question marks over what the best course of treatment will be for the 35-year-old's foot problem.

In announcing his withdrawal from the rest of the campaign, Nadal declared a foot issue that he has been bothered by since 2005 was behind his decision.

The Spaniard took a break after losing a French Open semi-final to Novak Djokovic, skipping Wimbledon and the Olympic Games.

He attempted to make a return for the hard-court season but lost his second match in Washington to South African Lloyd Harris.

Moya, who was also briefly a world number one, said Nadal had managed to prolong a career that was in doubt 16 years ago, thanks to insoles and treatment.

"But this year the story has changed in many training sessions," Moya said. "He could not finish them and we had to change and ease intensity for the foot, thinking about the tournaments.

"He has been in pain for months and there comes a time when he cannot take it anymore. In the last match he played practically lame.

"The best thing was to stop, rest the foot and refresh the head."

Speaking to Spanish broadcaster Onda Cero's El Transistor show, Moya said: "It is not known where this injury comes from. There is a diagnosis but it is not clear which is the best treatment.

"Rafa's main objective is to regain sensations in his feet and in his head, because stumbling all year round has not helped him."

Andrey Rublev finally got the better of compatriot Daniil Medvedev after a flashpoint involving a courtside camera in the Western and Southern Open semi-finals.

Rublev will now face Alexander Zverev in the decider, having ended Medvedev's bid for a Toronto-Cincinnati double.

Medvedev had never even dropped a set to his fellow Russian in four prior ATP Tour meetings and appeared to be on course for another dominant victory when he took the first set.

But the world number two clattered into a camera early in the second and all momentum was soon lost.

Medvedev complained about the positioning of the camera, claiming it had caused a hand injury and aiming a kick at the lens.

He swiftly called for treatment as his performance started to fall well below his lofty standards, with Rublev finally able to win a set after breaking in an epic 15-minute game.

A series of unforced Medvedev errors allowed Rublev to break again in the decider and seal a stunning 2-6 6-3 6-3 triumph.

Third seed Zverev fought back from a double break down in the final set to progress to the final with a 6-4 3-6 7-6 (7-4) win over second seed Stefanos Tsitsipas.

The epic match lasted two hours and 41 minutes, with Zverev responding strongly after appearing unwell to book his spot in the final against Rublev.

Rublev gets his Daniil degree

Asked to reflect on finally toppling Medvedev, Rublev told Amazon: "It's always tough to play against Daniil and to beat him.

"I think it gives me a bit more confidence that I can play against him, I can compete against him. There are still so many things to improve, but it's like I've passed university."

The victory came as a relief, with Rublev believing he was unfortunate even to be trailing in the first set.

"Inside I was thinking, when I was 6-2, the score shouldn't be like this," he said.

"The points were really tight, some little outs, little mistakes, some good shots from Daniil. The score was not real [in] the first set.

"Even the third set, I won 6-3 but the match was so intense. You saw so many rallies, so many long rallies, and it was so tough.

"It was a super mental match, a super physical match, exactly like a chess match."

Zverev's Novak mentality

Tokyo 2020 gold medalist Zverev had trailed 4-1 in the third set against Tsitsipas, but fought back with two breaks before winning in a tie-break.

"After I did the first break back I thought 'OK I have the chances'," Zverev said during his on-court interview. "I felt like he was not serving bombs. I felt like I was always in the rallies but I was losing the rallies because I was a bit low energy, so I started being a bit more aggressive, a bit of the Novak mentality that I had against him at the Olympics as well."

Zverev has a 4-0 record against final opponent Rublev but he was wary of his opponent.

"Favourite or not, I think if you're in the final, there's no easy opponent," he said. "Today he played incredible beating Medvedev."

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."

Rafael Nadal has curtailed his 2021 ATP Tour season due to a long-term foot injury but insists he is working towards a return.

Nadal, 35, has played only twice since losing the French Open semi-final to Novak Djokovic in May.

The Spaniard skipped Wimbledon and the Tokyo Olympics and had withdrawn from this week's Western and Southern Open before the US Open.

Nadal will not now compete in the final major of the season either, while great rival Roger Federer is also out for an extended period.

It clears a path for Novak Djokovic – the third man tied on 20 grand slam titles – to win a record-breaking 21st championship at Flushing Meadows while completing a remarkable calendar Grand Slam.

Djokovic could yet have competition again in the years to come, though, as Nadal is not yet calling time on a glittering career.

In making his latest announcement on social media on Friday, Nadal revealed he has been dealing with his injury since 2005 but has not let it halt him yet.

"Hello everyone," he wrote on his Twitter page. "I wanted to inform you that unfortunately I have to end the 2021 season.

"Honestly, I've been suffering a lot more than I should with my foot for a year and I need to take some time.

"After having discussed it with the team and family, this decision has been made and I think it is the way forward to try to recover and recover well.

"It's a year that I've missed things that matter a lot to me, like Wimbledon, like the Olympics, how the US Open is going to be now, like many other events that are also important to me.

"And in view of the fact that during this last year I have not had the ability to train and prepare and compete in the way that I really like to do it, in the end, I come to the conclusion that what I need is time to recover, change a series of things, try to understand what has been the evolution of my foot in recent times.

"It is not a new injury, it is an injury that I have had since 2005 and it has not prevented me from developing my sports career during all these years.

"If it is true that I have had a season where things are not going as they should, as we would all like, it is time to make decisions, seek a slightly different type of treatment to find a solution to this problem or at least improve it in order to continue to have options for the next few years.

"I have the maximum enthusiasm and predisposition to do whatever it takes to recover the best possible form to keep competing for the things that really motivate me and the things that I've done all these years.

"I am convinced that with the recovery of the foot, and obviously a very important daily effort, this can be achieved. I will work as hard as I can to make it happen.

"Thank you in advance for all the support, understanding and all your expressions of affection that are very important and more in difficult times like these.

"I promise you what I am going to do is work hard to try to continue enjoying this sport for a while longer. A big hug to all."