
Juan Martin del Potro of Argentina returns a ball to Rafael Nadal of Spain during the men's singles semifinal match at the 2017 U.S. Open in New York, the United States, Sept. 8, 2017. Juan Martin del Potro lost 1-3. (Xinhua/Wang Ying)

Juan Martin del Potro of Argentina returns a ball to Rafael Nadal of Spain during the men's singles semifinal match at the 2017 U.S. Open in New York, the United States, Sept. 8, 2017. Juan Martin del Potro lost 1-3. (Xinhua/Wang Ying)