World number one Novak Djokovic is still battling a wrist injury just days out from the US Open.
The Serbian withdrew from the Western and Southern Open because of the problem, and it remains a worry ahead of a first-round clash against Jerzy Janowicz at Flushing Meadows.
Djokovic, who is the defending champion in New York, said he was still below full fitness.
"The wrist hasn't been in an ideal state for the last three and a half weeks," he said on Friday.
"But I'm doing everything in my power with the medical team to make sure that I'm as close to 100 per cent as possible."
The 12-time grand slam champion claimed the title in Toronto following his early Wimbledon exit, before suffering a shock first-round loss at the Rio Olympics.
Djokovic said private matters had impacted him at the All England Club, where he fell in the third round to Sam Querrey.
"Again, I am in a position, like everybody else, like all of you, we all have private issues and things that are more challenges than issues, more things that we have to encounter and overcome in order to evolve as a human being," he said of the issue, without going into detail.
"That was the period for me. It happened right there, was resolved and life is going on like everything else."