Switzerland's Timea Bacsinszky has withdrawn from the US Open due to a lingering hand injury, the world number 24 has said.
Bacsinszky, who will also miss this month's Connecticut Open in New Haven, was carrying a thigh injury during Wimbledon last month but said on Wednesday she had also been troubled by her hand since last year.
"Unfortunately, I was forced to pull out of New Haven and the U.S. Open," Bacsinszky, who reached the French Open semi-finals earlier this year, said on her Instagram account.
"My thigh is now much better, but I still need to undertake a few exams for my hand. I cannot express how sad I am to announce such bad news, but my priority... is to let my body heal completely and take all the time needed in order to do so."
The US Open runs from Aug 28 to September 10 at Flushing Meadows, New York.
Del Potro makes winning return, Muguruza through
Juan Martin del Potro made a winning return to the Cincinnati Open on Tuesday when the Argentine ground out a 3-6, 7-6(1), 6-0 victory over 10th-seeded Czech Tomas Berdych to reach the second round on Tuesday.
The 28-year-old, back in Cincinnati after a four-year absence from the US Open warmup event, powered down 17 aces to rally past Berdych after he surrendered the opening set following a listless start.
Berdych found his rhythm early in the match and broke Del Potro for a 3-1 lead and did not lose a point on his powerful serve until the 10th game.
But as Del Potro, a semi-finalist at the tournament in 2012 and 2013, worked his way back into the match, Berdych slowly began to lose confidence and failed to win a single game in the deciding set.
"During the second set, in the end, I played my best tennis," 2009 US Open champion Del Potro told reporters. "I hit so sure with my forehand. I made good serves and I took all my chances to win.
"Mentally, I was strong enough to keep fighting and I think he got down after losing that second set. Then, when I broke his serve early in the third (set), my game started improving and I played much better than him."
Del Potro advances to meet American qualifier Mitchell Krueger in the second round.
Australian Nick Kyrgios also opened his campaign with a welcome victory as the world number 23 beat Belgian ninth seed David Goffin 6-2, 6-3 in the afternoon heat to reach the second round.
Other than in the first game when he had to climb out of a 0-40 hole, Kyrgios experienced few problems on serve and even secured three breaks against Goffin, who had to take a medical time out for a knee injury during the match.
"He obviously wasn't at 100 percent today but you know I'm not at 100 percent either, so it was a bit of a battle," said Kyrgios, who has struggled with an array of injuries throughout the season.
"But I served well at crucial moments. I'm feeling okay. I think as long as I can keep putting in performances like these and being able to compete I think I'm okay."
In other action, third seed Dominic Thiem of Austria was barely tested in his 6-3, 6-2 second-round win over Italy's Fabio Fognini, while Jack Sock beat fellow American Tommy Paul 6-3, 6-3 to reach the round of 16.
Earlier in the day, big-serving Canadian Milos Raonic, the sixth seed, announced his withdrawal from the tournament due to a lingering left wrist injury.
Muguruza powers into round of 16 at Cincinnati
Garbine Muguruza got her final US Open tune-up event off to a flying start as the Wimbledon champion stormed by Brazilian qualifier Beatriz Haddad Maia 6-2, 6-0 to reach the third round of the Cincinnati Open on Tuesday.
Second seed Simona Halep overcame an early deficit to beat American qualifier Taylor Townsend 6-4, 6-1 and also reach the third round, while Venus Williams beat Alison Riske 6-2, 6-0 to advance to the second.
French Open champion Jelena Ostapenko was upset 6-4, 6-2 in the first round by unseeded Serbian Aleksandra Krunic and Agnieszka Radwanska, seeded 10th, was another to suffer an early exit, losing 6-4, 6-4 to German Julia Gorges.
Spanish fourth seed Muguruza, fresh off a quarter-finals loss to eventual winner Elina Svitolina at Toronto last week, needed only 65 minutes to earn the straight sets win over Haddad Maia and book her spot in the round of 16.
After trading breaks with Haddad Maia over the course of the first four games, Muguruza found another gear and went on to win the final 10 games of the match.
"I felt like a lot of games were super tight. She's super tall, big serve with big shots. It was a strange result, because the match was pretty good," said world number six Muguruza.
"I feel like yesterday I was playing on the grass, and now I'm here. I'm happy to be in the third round here."
Muguruza now awaits the winner of Wednesday's clash between American 16th seed Madison Keys and Russian Daria Kasatkina.
Romanian Halep, the 2015 Cincinnati runner-up, fell behind early but reeled off four consecutive games, including two love service holds, to clinch the opening set and remained in control the rest of the way.
Halep will next face Latvia's Anastasija Sevastova, who earlier rallied to beat China's Peng Shuai 3-6, 6-4, 6-2.
Venus overpowers Riske at Cincinnati Masters
Ninth-seeded Venus Williams used her powerful serve and pinpoint shot making to defeat fellow American Alison Riske 6-2, 6-0 in the first round of the Cincinnati Masters on Tuesday.
Riske put a volley wide to end a seven-minute game and hand the first set to Williams on a sunny day on center court at the Lindner Family Tennis Center.
An early break in the second set put the 37-year-old Williams in complete control and she cruised to victory.
Fashion-conscious Williams' biggest struggle on the court may have been with her jewelry after her hoop earing fell off at one point and later got tangled with her necklace.
The win sets up a second round battle between Williams and Australian Ashleigh Barty, who defeated American Varvara Lepchenko 6-4, 6-4 earlier on Tuesday.
Paes-Zverev crash out of Cincinnati Open
India's Leander Paes and his German partner Alexander Zverev went down to the Spanish duo of Feliciano Lopez and Marc Lopez in a men's doubles first round match to bow out of the Cincinnati Open.
The Indo-German pair fought hard before losing 6-2, 6-7(2), 6-10 to their Spanish rivals in a closely-fought contest, which lasted an hour and 21 minutes.
The Spaniards will next take on fourth seeded American twins Bob and Mike Bryan in the second round.
Meanwhile, Rohan Bopanna and Ivan Dodig of Croatia have got a first round bye.
'Last two years have taken heavy toll on Murray'
The last two years on the relentless ATP Tour have taken their toll on Andy Murray, the three times Grand Slam champion's mum Judy told Reuters.
Murray, Wimbledon winner in 2013 and 2016, crashed out of the tournament in the quarter-finals this year as a hip injury got the better of him.
He has not played since and is racing to be fit in time for the US Open, where he won his first Grand Slam title in 2012. The tournament gets underway later this month.
"The last two years have taken a lot out of him," Judy Murray, herself a coach who nurtured her son's interest in tennis from a young age, said at the Edinburgh Book Festival.
"But the tennis calendar is relentless, it's 11 months of the year, there's hardly any gaps to have a rest and I kind of feel that it's all caught up on him."
The ATP Tour, which runs from the start of January to late November, offers little respite for players, whose ranking can suffer if they miss tournaments.
Asked if Murray, who is set to lose his number one ranking to Rafael Nadal next week, would be playing at the US Open she said: "I hope so, I hope so," before adding that she does not act as an official adviser.
"I advise him to rest, for sure, but since when do you listen to your mum?" she joked.
Asked about seventh-ranked Johanna Konta, who this year became the first British woman to reach the last four at Wimbledon since 1978, Murray said she believed she had great potential.
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