Cincinatti - Argentinian title holder Juan Martin del Potro has pulled out of this year's US Open as he has not fully recovered from a wrist injury, a US Tennis Association (USTA) spokesman told AFP on Saturday.
"Juan Martin Del Potro has just withdrawn. It is very unfortunate. I am sure he is disappointed not to be able to defend his title but we look forward to seeing him in New York next year," Chris Widmaier, USTA's managing director of communications, said at the current ATP tournament in Cincinnati.
Del Potro has not played since January 24, when he lost to Croatian Marin Cilic at the Australian Open.
In May, he underwent surgery for a persistent wrist problem and only recently returned to hitting balls.
Del Potro won his first Grand Slam title by rallying to beat five-time US Open champ Roger Federer in five sets in last year's final at Flushing Meadows.
Del Potro's withdrawal comes the day after women's world number one Serena Williams pulled out of the women's event at the US Open because she is still recovering from surgery to repair cuts on her right foot.
The US Open begins August 30.