NEW YORK, NY - SEPTEMBER 06: Juan Martin Del Potro of Argentina reacts at the net during his men's singles quarterfinal match against Novak Djokovic of Serbia on Day Eleven of the 2012 US Open at USTA Billie Jean King National Tennis Center on September 6, 2012 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Clive Brunskill/Getty Images)
