Spanish player Rafael Nadal returns the ball to Japanese player Kei Nishikori during the men’s singles final tennis match of the Madrid Masters at the Magic Box (Caja Magica) sports complex in Madrid on May 11, 2014. Rafael Nadal won his fourth title at the Madrid Masters, 2-6, 6-4, 3-0 when Kei Nishikori retired with a lower back injury. AFP PHOTO / DANI POZO (Photo credit should read DANI POZO/AFP/Getty Images)