Li Na of China celebrates her victory over Francesca Schiavone of Italy at women's singles fourth round match of the U.S. Open tennis tournament in New York, the U.S., Sept. 6, 2009. Li won the match 2-0. (Xinhua/Shen Hong)

Li Na of China signs for fans after her victory over Francesca Schiavone of Italy at women's singles fourth round match of the U.S. Open tennis tournament in New York, the U.S., Sept. 6, 2009.(Xinhua/Shen Hong)

Li Na of China reacts after winning over Francesca Schiavone of Italy at women's singles fourth round match of the U.S. Open tennis tournament in New York, the U.S., Sept. 6, 2009.(Xinhua/Shen Hong)

US's Serena Williams returns a shot to Slovakia's Daniela Hantuchova during women's singles fourth round match at the U.S. Open tennis tournament in New York, the U.S., Sept. 6, 2009.(Xinhua/Shen Hong)

US's Serena Williams serves to Slovakia's Daniela Hantuchova during women's singles fourth round match at the U.S. Open tennis tournament in New York, the U.S., Sept. 6, 2009. Serena Williams won the match 2-0. (Xinhua/Shen Hong)

US's Serena Williams returns a shot to Slovakia's Daniela Hantuchova during women's singles fourth round match at the U.S. Open tennis tournament in New York, the U.S., Sept. 6, 2009.(Xinhua/Shen Hong)