NEW YORK, NY - SEPTEMBER 6 :   Marin Cilic of Croatia returns the ball to Roger Federer of Switzerland during their men's singles semifinal match on Day 13 of the 2014 US Open at the USTA Billie Jean King National Tennis Center in New York, United States on September 6, 2014. (Photo by Bilgin Sasmaz/Anadolu Agency/Getty Images)