
Novak Djokovic of Serbia celebrates after defeating John Isner of the United States during their men's singles quarterfinal at the China Open tennis tournament in Beijing, China, Oct. 9, 2015. Djokovic won 2-0. (Xinhua/Xing Guangli)

Novak Djokovic of Serbia celebrates after defeating John Isner of the United States during their men's singles quarterfinal at the China Open tennis tournament in Beijing, China, Oct. 9, 2015. Djokovic won 2-0. (Xinhua/Xing Guangli)