Nishikori of Japan celebrates after defeating Wawrinka of Switzerland in their quarter-final match at the 2014 U.S. Open tennis tournament in New York

Kei Nishikori of Japan celebrates after defeating Stan Wawrinka of Switzerland in their quarter-final match at the 2014 U.S. Open tennis tournament in New York, September 3, 2014. REUTERS/Mike Segar