Francesca Schiavone of Italy hits a retu

Francesca Schiavone of Italy hits a return during her women's match against Chanelle Sheepers of South Africa at the 2011 US Open tennis tournament on September 3, 2011 in New York. AFP PHOTO/DON EMMERT (Photo credit should read DON EMMERT/AFP/Getty Images)

Caroline Wozniacki of Denmark (1) plays

Caroline Wozniacki of Denmark (1) plays against Vania King of the United States during their Women's match at the USTA Billie Jean King National Tennis Center in New York on September 3, 2011. AFP PHOTO / TIMOTHY A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images)

Vania King of the United States plays ag

Vania King of the United States plays against Caroline Wozniacki of Denmark (1) during their Women's match at the USTA Billie Jean King National Tennis Center in New York on September 3, 2011. AFP PHOTO / TIMOTHY A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images)

Serbian tennis player Ana Ivanovic retur

Serbian tennis player Ana Ivanovic returns a shot to Sloane Stephens of the US during their Women's US Open 2011 third round match at the USTA Billie Jean King National Tennis Center in New York on September 3, 2011. AFP PHOTO/Emmanuel Dunand (Photo credit should read EMMANUEL DUNAND/AFP/Getty Images)

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.

2011 US Open - Day 6

during Day Six of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2011 in the Flushing neighborhood of the Queens borough of New York City.