Del Potro into US Open final after defending champion Nadal retires in semis

Juan Martin del Potro of Argentina hits a return during the men's singles semifinal match against Rafael Nadal of Spain at the 2018 US Open tennis tournament in New York, the United States, Sept. 7, 2018. Juan Martin del Potro won as Nadal retired due to injury. (Xinhua/Liu Jie)