NEW YORK, NY - SEPTEMBER 07: Roger Federer of Switzerland returns a shot against John Isner of the United States during their Men's Singles Fourth Round match on Day Eight of the 2015 U.S. Open at the USTA Billie Jean King National Tennis Center on September 7, 2015 in New York City. (Photo by Cem Ozdel/Anadolu Agency/Getty Images)
