Roger Federer has admitted that he was outplayed by Kei Nishikori following his 4-6 6-1 2-6 Madrid Open defeat to the world number 14.
The defending champion expressed his disappointment with the result, but conceded that he was beaten by a better player.
"I'm disappointed with my match. Today Nishikori played better and the best man won," BBC Sport quotes Federer as saying.
Nishikori said after the game: "It's the biggest win for me, especially on clay."
The result marks the Japanese player's first career victory over Federer.