NEW YORK, NY - SEPTEMBER 07: Juan Martin del Potro of Argentina returns a shot to Stan Wawrinka of Switzerland during their Men's Singles Quarterfinals Match on Day Ten of the 2016 US Open at the USTA Billie Jean King National Tennis Center on September 7, 2016 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Hewitt/Getty Images)
