Juan Martin del Potro, of Argentina, acknowledges the cheering crowd as he leaves the the court after losing 7-6 (5), 4-6, 6-3, 6-2 to Stan Wawrinka, of Switzerland, during the quarterfinals of the U.S. Open tennis tournament, early Thursday, Sept. 8, 2016, in New York. (AP Photo/Seth Wenig), APTOPIX