Nadal wins Madrid Masters
The world number one led 2-6 6-4 3-0 when a hobbling Nishikori - who had led by a set and a break - pulled out.
Nadal, 27, becomes the first man to win four Madrid titles and extends his Masters 1000 record to 27 victories.
The Spaniard had lost in the quarter-finals of his previous two tournaments, in Monte Carlo and Barcelona. (QNA)