Great Britain's Dan Evans and Cameron Norrie suffered first-round exits for the second week running as their preparations for the US Open took a hit with early losses at the Cincinnati Open.
Evans, currently ranked 28th in the world, secured the biggest title of his career earlier this month as he won the Washington Open but has lost both of his matches since.
The 33-year-old was beaten by Canada's Gabriel Diallo at the Canadian Open last week and on Tuesday went down 6-4 6-3 to Italy's Lorenzo Musetti in a game delayed by a day due to rain.
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World No 15 Norrie, meanwhile, followed his defeat to Alex de Minaur in Toronto with a 3-6 6-4 6-3 reverse against Gael Monfils in Cincinnati and has not won more than one match at an event since reaching the quarter-finals at Queen's in June.
There is no more British interest in the men's singles with Andy Murray withdrawing from his first-round encounter against Karen Khachanov due to an abdominal strain.
The 36-year-old is aiming to recover ahead of the US Open, which is live on Sky Sports from August 28.
Evans was broken early in the first set by world No 18 Musetti but then pegged his opponent back to 4-4 before he was broken for a second time.
Musetti then served out the set in the next game despite Evans earning two break points of his own.
The Brit handed Musetti an early advantage in the second set with a double fault and the Italian closed out the match to book a meeting with third seed Daniil Medvedev in the last 32.
Wozniacki beaten as comeback from retirement continues
In the women's event, former world No 1 and 2018 Australian Open champion Caroline Wozniacki lost 6-4 6-4 to Varvara Gracheva of France as she continued her return from retirement.
Wozniacki, 33, who quit professional tennis in 2020 to start a family, won one match in Canada last week before being eliminated in the round of 32 by Wimbledon champion Marketa Vondrousova.
The Dane carved out nine break points against Gracheva but failed to convert any of them as her opponent advanced to the round of 32 in Ohio, alongside Vondrousova, who saw off fellow Czech Kateřina Siniaková 7-6 6-4.
Wozniacki said: "I still have about 10 days to prepare for the US Open. There are quite a few things that I feel like I need to do better.
"Last week I thought I was pretty pleased about where I was. I think this week I don't feel like my timing is exactly where I want it to be, so I'm just going to go back and work hard.
"I believe in myself. Obviously it's just taking me a little bit of time just to get used to the matches again and competing in real tournaments.
"I don't really feel the expectations from everyone else. I think I have always been tough on myself. I'm looking for perfection, which is not possible in this sport."
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