(CNN) -- Rafael Nadal won his first European clay title of the season and 27th Masters tournament victory of his career at the Madrid Open after his opponent Kei Nishikori was forced to retire through injury.
Nadal had won seven straight games to lead 3-0 in the third set when the match was halted having lost the first set 6-2 and come from a break down to win the second 6-4.
Nishikori had struggled with a back spasm in Saturday's dramatic semifinal victory over Nadal's fellow Spaniard, David Ferrer, and the injury returned to haunt him on Sunday.
Although disappointed to lose his first Masters final in in such an unfortunate manner, the Japanese can take comfort from his performances this week which will see him break into the world top 10 for the first time when the latest rankings are released Monday.
Nishikori out-played Nadal for a set and a half with some aggressive shot making and big winners.
After the trainer was called seven games into the second set, however, it was clear that Nishikori's movement was inhibited.
Nadal capitalized to break twice and level the match at a set apiece.
The third set was an anti-climax by comparison with Nadal easing ahead of his injured opponent before Nishikori decided he couldn't continue.
"I am very disappointed about what happened today in this final," said Nishikori after the match.
"Unfortunately, I was hurting already and I tried to fight but Rafa was too good today, so congratulations to him."
As ever, Nadal was gracious in victory.
"I'm very sorry for Nishikori. He's an unbelievable player that will fight to be in London (at the ATP World Tour Finals)," he said.
"Winning at home is always more special than winning anywhere. Having the chance to play in front of your home crowd... is unforgettable for me," he added.
Sharapova bounces back
Earlier, Maria Sharapova recovered from a horrendous start to defeat Romania's Simona Halep 1-6, 6-2, 6-3 to claim the women's title.
The Russian lost the first four games of the match to the World No. 5 and conceded the first set in less than half-an-hour.
Sharapova turned things around as the game progressed and has now won seven of her last nine titles on a clay, a surface once far from her favorite.
Speaking on court after the match, the 27-year-old said: "Last year I lost in the finals and I really wanted to go one extra step this year, and it's just been such a fantastic week.
"Simona and I had played a couple of times before, but she's really on a different level now (having risen from 64th position in the world rankings this time last year). I don't know how I pulled it off."