2016 U.S. Open Tennis Tournament. New York. USA. [Getty Images]

2016 U.S. Open - Day 12 Stan Wawrinka of Switzerland in action against Kei Nishikori of Japan in the Men"u2019s Singles Semifinal match on Arthur Ashe Stadium on day twelve of the 2016 US Open Tennis Tournament at the USTA Billie Jean King National Tennis Center on September 9, 2016 in Flushing, Queens, New York City. (Photo by Tim Clayton/Corbis via Getty Images)

Corbis Sport Tim Clayton - Corbis