NEW YORK, NY - SEPTEMBER 11: Marin Cilic of Croatia returns a shot to Novak Djokovic of Serbia during their Men's Singles Semifinals match on Day Twelve of the 2015 US Open at the USTA Billie Jean King National Tennis Center on September 11, 2015 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)
