Dan Evans admitted he struggled with the mental as well as physical side of coronavirus as his sluggish recovery process left him fearing for his career.
The British No 1 arrived in New York on the back of four defeats in his last five matches since Wimbledon after
missing the Olympics because he contracted coronavirus.
Evans defied two minor rain delays to book his place in the third round of the US Open for the fourth time after beating American Marcos Giron in four sets, limping over the line despite a foot problem.
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After the match, Evans revealed the dread that he might never regain the fitness required to stay competitive at the top of the sport due to the virus.
Evans said: "I wouldn't say I lost confidence with my game but I lost the physical side of it and there are so many unknowns that you don't know if it's ever going to come back - do you get long Covid? So it was more of a mental thing.
"I put in some good work after Cincinnati with my trainer and hopefully I'm ready to go in the next round and the round after that. I will see how the body holds up."
Evans, who will next face Australia's Alexei Popyrin, incurred a foot problem at 4-3 down in the fourth set but he eventually managed to limp over the line.
Andy Murray's criticism of the bathroom breaks taken by his first-round opponent Stefanos Tsitsipas has led to talk of underhand tactics and Evans admitted he was eager to avoid similar accusations at such a critical point in the proceedings.
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He said: "My foot just got stuck in the ground and when I tried to move it, I tweaked it a little bit. I would normally have called the trainer but it goes without saying that this week is a difficult one.
"I would normally take a time-out but I just thought it was a pretty crucial point in the match where it could be questionable, and I wouldn't want people to think I was taking the time out to interrupt the flow of the match."
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