Novak Djokovic could meet Andy Murray in the semifinals at U.S. Open . Andy Murray and Serena Williams face a potential quarterfinal showdown in U.S. . Serena Williams begins against another grand slam winner , Rafael Nadal . While 12-time grand slam champion Nadal and 17-time winner Federer have tangled in the finals at the three other majors , they have never faced off in any round at the U.S. Open . Former winner Maria Sharapova pulled out of the tournament with a shoulder injury .
Novak Djokovic could meet Andy Murray in the semifinals at U.S. Open . Andy Murray and Serena Williams face a potential quarterfinal showdown in U.S. . Serena Williams begins against another grand slam winner , Rafael Nadal . Former winner Maria Sharapova pulled out of the tournament with a shoulder injury .