Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates defeating Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates defeating Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates defeating Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy is congratulated by Serena Williams of the US at the end of their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates winning a point against Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US celebrates winning a point against Roberta Vinci of Italy during their 2015 US Open semifinal match at the USTA Billie Jean King National Tennis Center in New York on Sept. 11, 2015. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US returns the ball to Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US celebrates winning a point against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena WilliamsI

Serena Williams of the US reacts while playing against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US returns the ball to Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US returns the ball to Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US approaches a shot while playing against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. (Photo credit JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates defeating Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates defeating Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena WilliamsNCI

Serena Williams of the US leaves the court after being defeated by Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena WilliamsI

Serena Williams of the US reacts while playing against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US reacts while playing against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

TUS Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US reacts while playing against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy returns the ball to Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy returns the ball to Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy returns the ball to Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy returns the ball to Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Roberta Vinci of Italy celebrates defeating Serena Williams of the US during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

US Open: Roberta Vinci Defeats Serena Williams

Serena Williams of the US reacts after losing a point to Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. Vinci won 2-6, 6-4, 6-4. (Photo JEWEL SAMAD/AFP/Getty Images)

Serena Williams

Serena Williams of the United States reacts after losing a point against Roberta Vinci of Italy during their US Open semifinal match on Sept. 11, 2015, in New York City. Vinci, ranked 43rd, shocked Williams 2-6, 6-4, 6-4, ending the world No. 1’s pursuit of a calendar year Grand Slam. (Photo by Maddie Meyer/Getty Images)

Serena Williams beaten at US Open

Serena Williams of the US reacts while playing against Roberta Vinci of Italy during their 2015 US Open Women's singles semifinals match at the USTA Billie Jean King National Tennis Center in New York on September 11, 2015. AFP PHOTO/JEWEL SAMAD (Photo credit should read JEWEL SAMAD/AFP/Getty Images)