Roger Federer vows to improve

Roger Federer has vowed to return to the practice court following his third-round defeat to Kei Nishikori at the Madrid Open.

The defending champion saw his comeback from a self-imposed two-week break dealt a blow on Thursday as he went down 4-6 6-1 2-6 to the world number 14.

"I've been very successful here, so clearly I'm disappointed and wish I could have done better this week," the Swiss is quoted as saying by Eurosport.

"It doesn't change my mindset going forward. I'm going to go back to the practice court, train hard and make sure I don't have these kind of days anymore."

Federer will return to action next week at the Rome Masters.