NEW YORK, UNITED STATES - SEPTEMBER 09: Novak Djokovic (C) of Serbia is in action against Gael Monfils (not seen) 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 in New York City, NY, USA on September 9, 2016. (Photo by Volkan Furuncu/Anadolu Agency/Getty Images)