Kei Nishikori of Japan controls the ball during the Madrid Open final tennis match against Rafael Nadal...
Kei Nishikori of Japan controls the ball during the Madrid Open final tennis match against Rafael Nadal of Spain May 11, 2014. Nadal won a second successive Madrid Open title when Nishikori was forced to retire in the third set of Sunday's final with an apparent back injury. REUTERS/Andrea Comas (SPAIN - Tags: SPORT TENNIS)