Rafael Nadal won his fourth title at the Madrid Masters, 2-6, 6-4, 3-0 when Kei Nishikori retired with a lower back injury.
The Japanese player won the first set and had the top seed in trouble after breaking to start the second set before the lower back problems which have bothered him all week began to kick in late in the second set.
Nadal held on to win his first title of the spring season over Nishikori, the champion last month at Barcelona.
The win comes just in time for Nadal with the defence of his French Open title starting in a fortnight.
Nadal had won all six previous meetings -- 14 consecutive sets -- against Japan's top player, who will move into the top 10 on Monday.