Result: Andrea Petkovic battles into third round

Tenth seed Andrea Petkovic has advanced into the third round of the US Open after a comeback against China's Zheng Jie.

The German, who had her right knee in a bandage, was unable to match her opponent in the first set and lost 6-3.

Zheng stormed to 3-0 in the second and it looked as if the German was about to crash out of the tournament before she mounted her comeback.

She won the next six games of the second to level the match, before taking the final set 6-3 to set up a clash with Italy's Roberta Vinci.