Madrid ( Spain), May 12 - World Number One Rafael Nadal won his first European clay court title here at the Madrid Masters on Sunday, after a back injury forced Japan's Kei Nishikori to retire during the final.

According to the BBC, Nadal led 2-6 6-4 3-0 when a hobbling Nishikori, who had led by a set and a break, had to pull out of the match.

Nadal, 27, becomes the first man to win four Madrid titles and extends his Masters 1000 record to 27 victories.

Nadal has now won 44 clay-court titles and is just two away from equalling Argentine great Guillermo Vilas's all-time record of 46 on the surface

He will now head to next week's Rome Masters before moving on to Paris at the end of the month for the French Open, where he is an eight-time champion.

Nadal said that he felt sorry for Nishikori and recalled that he had faced a similar situation in Australia this year, and realised that latter's disappointment at having to quit in the middle of such an important match.

Nishikori, 24, went close to causing a major upset in Madrid, only to injure his back during a service game at 4-3 in the second set. He had required several bouts of treatment during Saturday's three-hour win over David Ferrer, but this time the trainer was unable to get the Japanese player back to a competitive state. (ANI)