Wawrinka of Switzerland hits a return to Nishikori of Japan during their quarter-final match at the 2014 U.S. Open tennis tournament in New York

Stan Wawrinka of Switzerland hits a return to Kei Nishikori of Japan during their quarter-final match at the 2014 U.S. Open tennis tournament in New York, September 3, 2014. REUTERS/Eduardo Munoz