Li Na, from China, hits a backhand to Venus Williams, of the United States, during a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Li Na, from China, hits a forehand against Venus Williams during a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Serena Williams, left, watches her sister Venus Williams, right, play in a semifinals match against Li Na, from China, at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Venus Williams volleys against Li Na, from China, during a semifinals match at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Venus Williams has her back worked on by a trainer during a semifinals match against Li Na, from China, at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Venus Williams hits a backhand shot against Li Na, from China, during a semifinals match at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Venus Williams grimaces during a semifinals match against Li Na, from China, at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. Na won 7-5, 3-6, 6-1. (AP Photo/Al Behrman)

Li Na, from China, reacts after defeating Venus Williams 7-5, 3-6, 6-1, in a semifinals match at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Li Na, from China, reacts after defeating Venus Williams 7-5, 3-6, 6-1 in a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Petra Kvitova, from the Czech Republic, hits a forehand against Angelique Kerber, from Germany, during a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Angelique Kerber, from Germany, hits a forehand against Petra Kvitova, from the Czech Republic, during a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Angelique Kerber, from Germany, clenches her fist after winning a game against Petra Kvitova, from the Czech Republic, during a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)

Petra Kvitova, from the Czech Republic, hits a backhand to Angelique Kerber, from Germany, during a semifinal at the Western & Southern Open tennis tournament, Saturday, Aug. 18, 2012, in Mason, Ohio. (AP Photo/Al Behrman)