New York: Troubled by injury and a private matter that affected him at Wimbledon, world No.1 Novak Djokovic concedes that time is against him as he prepares to end his grand slam season on a high at the US Open.

After he was beaten in the third round at Wimbledon by American Sam Querrey, Djokovic said he was "not really" 100 per cent. On Friday, he described it as a personal issue.

Reigning US Open men's champion Novak Djokovic has had turbulent times recently. Credit:AP

"It was nothing physical, it was not an injury," the 29-year-old Serb said. "It was some other things that I was going through privately. But it was nothing linked to the wrist injury I got in Rio.

"We all have private issues and things that are more challenges than issues, things we have to encounter and overcome in order to evolve as a human being. That was the period for me. Was resolved and life is going on like everything else."