Defending champion Dominic Thiem has withdrawn from the US Open and will miss the rest of the season.
Thiem has failed to recover from a wrist injury suffered while contesting the Mallorca Open in June.
In a statement, the 27-year-old Austrian said: "Having spent a week training on court, I still felt pain in my wrist and I knew that it was not 100 per cent.
"I went to see my doctors again and we have decided to follow a conservative treatment, giving the injury more time to recover.
"I'm very disappointed not to be able to defend my US Open title and to miss the rest of the season.
"But I know this is what I have to do. I have a long career ahead of me, so I will only come back once I'm fully recovered and in good shape to compete."
Thiem won his maiden grand slam title at Flushing Meadows last year, coming from two sets down to beat Germany's Alexander Zverev in the final.
However, he has struggled for form and fitness this year, going out in the first round of the French Open and missing both Wimbledon and the Tokyo Olympics.
He joins Roger Federer in pulling out of the US Open, with the 20-time grand slam champion opting to undergo knee surgery.
