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Madrid, Spain (SportsNetwork.com) - Rafael Nadal captured his fourth career Madrid Open title when Kei Nishikori retired during the third set of Sunday's final because of an apparent back injury.

Nadal roared back from down 4-3 in the second set, breaking Nishikori twice to even the match, which ended in a 2-6, 6-4, 3-0 win.

Nishikori was examined by a trainer after the seventh game of the second set and appeared to be laboring through back pain. The Japanese No. 1 was bidding to become the first Asian to win a Masters 1000 title.

Instead, top-ranked Nadal won his record 27th ATP World Tour Masters title, improving to 7-0 all-time against Nishikori. He earned $970,000 for the win.

It was the first time Nishikori, 24, faced the 13-time grand slam champion in a match that came later than the round of 16. He won a set against Nadal for the first time since their initial meeting at Queen's Club in 2008.

Nadal also won the Madrid title in 2005, 2010 and last year.