Rafael Nadal won his fourth Madrid Open title on Sunday after Kei Nishikori was forced to withdraw with an injury when trailing, 2-6, 6-4, 3-0, in the final.
Nishikori's powerful groundstrokes helped him win the first set against the top-ranked Nadal, who couldn't find a way to counter his Japanese opponent.
But Nadal slowly clawed back into the match at the Magic Box and broke twice in the second set to even the match.
But Nishikori was in obvious discomfort in the third and received treatment on his lower back during a medical timeout before eventually retiring.
Nadal recovered from two recent quarterfinal losses on clay to win his second title on the surface this year.