Rafael Nadal completed the defence of his Madrid Open title when Kei Nishikori was forced to retire due to injury in the deciding set of the final.
Japan's Nishikori, bidding for back-to-back titles after his maiden claycourt win in Barcelona last week, led by a set and a break at 6-2 4-2 before his body let him down.
Top seed Nadal broke back to level the second set at 4-4 and Nishikori required treatment on his back, which had also troubled him during his semi-final victory over David Ferrer.
The tide had now turned, Nadal broke again to take the second set 6-4 and was 3-0 up in the third when 10th seed Nishikori decided he could not continue.
The 27th Masters title of Nadal's career ends his mini-slump after he started the European claycourt swing - which he has dominated for the past decade - with consecutive quarter-final exits in Monte Carlo and Barcelona.
Nishikori, who was playing in his first Masters series final and will break into the top 10 for the first time on Monday, completely outplayed an out-of-sorts Nadal for the a set-and-a-half.
Nadal began the final with six successive points but Nishikori saved a break point and then exploited his Spanish opponent's lack of rhythm by forging ahead 5-1.
Nishikori quickly closed out the opening set and then broke again at the start of the second.
Nadal had three chances to break back in the next game, only to miss them all, to the bemusement of himself and the Madrid crowd.
But Nishikori called the trainer to have his back massaged and it soon became clear that his movement was becoming compromised.
He saved two break points but not a third and, although he battled on for a while after further treatment, it had become a lost cause.
Nishikori confirmed afterwards he had carried the back injury into the final, saying: "I am very disappointed about what happened today.
"Unfortunately, I was hurting already and I tried to fight but Rafa was too good today so congratulations to him.
"It's been a great few weeks for me in Spain. I won in Barcelona and now here the final in Madrid so it's becoming like a second home to me."