Juan Martin del Potro Pictures
NEW YORK, NY - SEPTEMBER 07: Juan Martin del Potro of Argentina celebrates victory after Rafael Nadal of Spain is forced to retire due to injury in his men's singles semi-final match on Day Twelve of the 2018 US Open at the USTA Billie Jean King National Tennis Center on September 7, 2018 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Elsa/Getty Images)