Tennis icon Novak Djokovic once again etched his name in the record books after his opening win over Learner Tien in the US Open.

Novak Djokovic looked tired. He looked hurt. And at times Sunday night, he just looked old. Djokovic overcame all that and improved to 19-0 in the first round of the US Open, battling through some leg troubles to beat Learner Tien 6-1,

Novak Djokovic wasn't at his fluent best as he returned to New York to play his first singles match since the Wimbledon semi-final last month. Djokovic was challenged by the American teenager Learner Tien at least in the second set,