Djokovic tested in New York
Novak Djokovic was the first of the title favourites to be tested at the US Open as he survived a close first set to defeat Benjamin Becker in the second round.
The world number one was well below his best in the early stages and German Becker served for the opening set at 5-4.
But he could not take either of two set points and from there Djokovic took control to win 7-6 (7/2) 6-2 6-2.
The Serb did not look comfortable at all during the first set and appeared to be breathing heavily.
Djokovic used to have a lot of problems with his breathing before switching to a gluten-free diet.
He said: "It was a struggle. It was different conditions from the first match, and I knew that he's a dangerous player. If he serves well and a high percentage, he can be a dangerous player. He's very solid from the baseline.
"Obviously his movement is not as good any more as it was, so I tried to move him around the court and open the court. That was my tactics.
"But it was very tough. There were a lot of unforced errors, very windy conditions. You couldn't really read and kind of predict where the ball was going to go, so you have to be very alert. At the start I had difficulty with my footwork.
"But I won the set and after that it was much, much better.
"I need to start the way I started in the first match, but my game is getting there. I feel that it was a big test for me today. It was a challenge, and I needed to overcome it. I'm glad I'm through in three."
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