Angelique Kerber of Germany returns a shot against Caroline Wozniacki of Denmark during their Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)
US Open: Day 11
Caroline Wozniacki of Denmark reacts against Angelique Kerber of Germany during their Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Al Bello/Getty Images)
US Open: Day 11
Angelique Kerber of Germany celebrates after defeating Caroline Wozniacki of Denmark with a score of 6-4, 6-3 in their Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Hewitt/Getty Images)
US Open: Day 11
Angelique Kerber of Germany hits a return against Caroline Wozniacki of Denmark during their 2016 US Open Womens Singles semifinal match at the USTA Billie Jean King National Tennis Center in New York on September 8, 2016. (Photo by Timothy A. Clary/AFP/Getty Images)
US Open: Day 11
Caroline Wozniacki of Denmark hits a return against Angelique Kerber of Germany during their 2016 US Open Womens Singles semifinal match at the USTA Billie Jean King National Tennis Center in New York on September 8, 2016. (Photo by Timothy A. Clary/AFP/Getty Images)
US Open: Day 11
Karolina Pliskova of the Czech Republic celebrates defeating Serena Williams of the United States 6-2, 7-6 during their Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Hewitt/Getty Images)
US Open: Day 11
Serena Williams of the United States reacts against Karolina Pliskova of the Czech Republic during her Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)
US Open: Day 11
Serena Williams of the United States pursues the ball against Karolina Pliskova of the Czech Republic during her Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)
US Open: Day 11
Serena Williams of the US hits a return against Karolina Pliskova of Czech Republic during their 2016 US Open Womens Singles semifinal match at the USTA Billie Jean King National Tennis Center in New York on September 8, 2016.
Serena Williams crashed out of the US Open on September 8, her semi-final defeat to Karolina Pliskova costing her a shot at a 23rd Grand Slam title and a record 187th straight week at number one. (Photo by Timothy A. Clary/AFP/Getty Images)
US Open: Day 11
Caroline Wozniacki of Denmark hits a return against Angelique Kerber of Germany during their 2016 US Open Womens Singles semifinal match at the USTA Billie Jean King National Tennis Center in New York on September 8, 2016. (Photo by Don Emmert/Getty Images)
US Open: Day 11
Serena Williams of the US reacts after losing a point against Karolina Pliskova of Czech Republic during their 2016 US Open Womens Singles semifinal match at the USTA Billie Jean King National Tennis Center in New York on September 8, 2016. (Photo by Timothy A. Clary/AFP/Getty Images)
US Open: Day 11
Karolina Pliskova of the Czech Republic reacts against Serena Williams of the United States during their Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Michael Reaves/Getty Images)
US Open: Day 11
Serena Williams of the United States returns a shot to Karolina Pliskova of the Czech Republic during her Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)
US Open: Day 11
Serena Williams of the United States serves to Karolina Pliskova of the Czech Republic during her Women's Singles Semifinal Match on Day Eleven of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Michael Reaves/Getty Images)
