US Open: Day 12

Novak Djokovic of Serbia serves to Gael Monfils of France during their Men’s Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Novak Djokovic of Serbia returns a shot to Gael Monfils of France during their Men’s Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Hewitt/Getty Images)

US Open: Day 12

Gael Monfils of France reacts after winning the third set against Novak Djokovic of Serbia during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Gael Monfils of France reacts against Novak Djokovic of Serbia during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Al Bello/Getty Images)

US Open: Day 12

Novak Djokovic of Serbia celebrates defeating Gael Monfils of France with a score of 6-3, 6-2, 3-6, 6-2 during their Men’s Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Hewitt/Getty Images)

US Open: Day 12

Novak Djokovic of Serbia reacts by ripping off his shirt while playing against Gael Monfils of France during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)

Bruce Willis At US Open

Bruce Willis (R) watches the 2016 US Open men's singles semifinal match between Gael Monfils of France and Novak Djokovic of Serbia at the USTA Billie Jean King National Tennis Center in New York on September 9, 2016. (Photo by Jewel Samad/AFP/Getty Images)

US Open: Day 12

Gael Monfils of France reacts against Novak Djokovic of Serbia during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Hewitt/Getty Images)

2016 US Open - Day 12

Gael Monfils of France returns a shot to Novak Djokovic of Serbia during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)

US Open: Day 12

Novak Djokovic of Serbia returns a shot to Gael Monfils of France during their Men’s Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Gael Monfils of France returns a shot against Novak Djokovic of Serbia during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)

US Open: Day 12

Gael Monfils of France reacts against Novak Djokovic of Serbia during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Chris Trotman/Getty Images for USTA)

Jon Hamm And Justin Bratha At US Open

Actors Jon Hamm (C) and Justin Bartha (R) are seen as Novak Djokovic of Serbia takes on Gael Monfils of France during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)

US Open: Day 12

Kei Nishikori of Japan returns a shot to Stan Wawrinka of Switzerland during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)

US Open: Day 12

Stan Wawrinka of Switzerland reacts to winning the second set against Kei Nishikori of Japan during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Chris Trotman/Getty Images for USTA)

US Open: Day 12

A general view as the court is dried during the Men's Singles Semifinal Match between Stan Wawrinka of Switzerland and Kei Nishikori of Japan on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Kei Nishikori of Japan reacts against Stan Wawrinka of Switzerland during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)

US Open: Day 12

Stan Wawrinka of Switzerland returns a shot against Kei Nishikori of Japan during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Chris Trotman/Getty Images for USTA)

US Open: Day 12

Stan Wawrinka of Switzerland celebrates defeating Kei Nishikori of Japan with a score of 4-6, 7-6, 6-4, 6-2 during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)

US Open: Day 12

Kei Nishikori of Japan reacts against Stan Wawrinka of Switzerland during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Al Bello/Getty Images)

US Open: Day 12

A general view is seen as fans watch Stan Wawrinka of Switzerland and Kei Nishikori of Japan during their Men's Singles Semifinal Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Jaime Lawson/Getty Images for USTA)

US Open: Day 12

Coco Vandeweghe and Rajeev Ram of the United States return a shot to Laura Siegemund of Germany and Mate Pavic of Croatia during their Mixed Doubles Final Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Coco Vandeweghe and Rajeev Ram of the United States return a shot to Laura Siegemund of Germany and Mate Pavic of Croatia during their Mixed Doubles Final Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Coco Vandeweghe (R) and Rajeev Ram (L) of the United States pose with the second place trophy after deing defeated by Laura Siegemund of Germany and Mate Pavic in their Mixed Doubles Final Match on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Alex Goodlett/Getty Images)

US Open: Day 12

Laura Siegemund (R) of Germany and Mate Pavic (L) of Croatia celebrate with the trophy after defeating Coco Vandeweghe of the United States and Rajeev Ram of the United States during their Mixed Doubles Final on Day Twelve of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2016 in the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)