
Philipp Kohlschreiber of Germany serves during the men's singles fourth round match against Roger Federer of Switzerland at the 2017 U.S. Open in New York, the United States, Sept. 4, 2017. Roger Federer won 3-0. (Xinhua/Wang Ying)

Philipp Kohlschreiber of Germany serves during the men's singles fourth round match against Roger Federer of Switzerland at the 2017 U.S. Open in New York, the United States, Sept. 4, 2017. Roger Federer won 3-0. (Xinhua/Wang Ying)