Nadal wins fourth Madrid title as Nishikori quits
Spanish player Rafael Nadal returns the ball to Japanese player Kei Nishikori during the men's singles final tennis match of the Madrid Masters at the Magic Box (Caja Magica) sports complex in Madrid on May 11, 2014 - by Pierre-Philippe Marcou
Japanese 10th seed Nishikori had taken the first set 6-2 and led 4-2 in the second before the back pain which had plagued him all week forced him to retire.
That allowed top seed Nadal to claim a 2-6, 6-4, 3-0 win for his 27th Masters title and 63rd career crown after one hour and 41 minutes on court.
Nadal had lost quarter-finals in Monte Carlo and Barcelona -- the event that Nishikori won last month -- and needed every bit of his fighting spirit to go through.
After taking a medical timeout after the ninth game of the second set after a 4-2 lead evaporated due to his condition, Nishikori, who moves into the top 10 on Monday for the first time, received treatment for his back on court.
But his body was broken and the top Asian on the ATP tour found it almost impossible to play on.
After making the attempt in a third set, he finally threw in the towel after three games.
"I'm very sorry for what happened today," said Nishikori. "This was my first Masters 1000 final and I was really excited to play.
"But I was hurting already and trying to fight. But Rafa was too good today."
Nishikori swept the opening set in a 35-minute surprise and began the second with a break of serve before his body began to betray him.
Nadal now stands 7-0 over Nishikori.
"I'm very sorry for what happened to you today and I hope you get better quickly. You played me tough today," said the Spanish champion, the first player to win four titles in the capital.
Nadal now heads to Rome next week to defend that trophy before he moves on to the French Open where he is an eight-time champion.