Argentina's Juan Martin del Potro returns the ball against Spain's Rafael Nadal during men's singles semifinal of Tennis at the 2016 Rio Olympic Games in Rio de Janeiro, Brazil, on Aug. 13, 2016. Juan Martin del Potro won 2-1. (Xinhua/Yue Yuewei)
Argentina's Juan Martin del Potro returns the ball against Spain's Rafael Nadal during men's singles semifinal of Tennis at the 2016 Rio Olympic Games in Rio de Janeiro, Brazil, on Aug. 13, 2016. Juan Martin del Potro won 2-1. (Xinhua/Yue Yuewei)