Roger Federer wins, to stay No. 1 for 300th week

"I'm trying to enjoy the efficiency of my serve," said Djokovic, who had three aces in one game in the first set. "I'm not very well known around the tour for big serving. But so far in this tournament, and also in Beijing, it has been working very well for me. It has been giving me a lot of free points, a lot of confidence into the matches."

Djokovic will play Tommy Haas of Germany, who defeated Djokovic's countryman, Janko Tipsarevic, 6-2, 6-1. Fourth-seeded Tomas Berdych of the Czech Republic defeated Sam Querrey of the United States 6-2, 6-7 (3), 6-4, and fifth-seeded Jo-Wilfried Tsonga beat Marcos Baghdatis of Cyprus 6-2, 7-6 (2).

Berdych will play fifth-seeded Jo-Wilfried Tsonga. The Frenchman downed Marcos Baghdatis of Cyprus 6-2, 7-6 (2).