Novak Djokovic has played down concerns over his fitness after he battled past Jerzy Janowicz in the first round of the US Open.

The world number one came into the tournament with an injury to his left wrist and he called for the trainer after just five games of his 6-3 5-7 6-2 6-1 victory over Janowicz to receive treatment on a problem with his upper-right arm.

The Serbian never looked comfortable as he battled his way through to the second round but insisted after the match that he is remaining positive.

Djokovic said: “It’s getting better and better each day. I’m glad that I’m experiencing that so hopefully, as the tournament progresses, I’ll reach my peak. “Calling for the medical time-out was just prevention.

It’s all good. To be honest, I take it day by day. That’s what I feel at the moment.” The 29-year-old will now face the Czech Republic’s Jiri Vesely in round two on Wednesday and he hopes to be back on song for the clash with the world number 49.

He added: “Tomorrow is a new day. I hope that I’ll feel good overall, so I’m able to perform at my best for the next match.”

Djokovic is the defending champion at Flushing Meadows and is available at 2.38 to successfully retain his title.