Federer ousted by Nishikori in Madrid; Nadal, Murray through

Second seed Federer, who had just returned to the tour after a two-month break, joins world number one Novak Djokovic in being eliminated early in the Spanish capital and his lack of match practice showed.

One break was enough for Nishikori to take the opening set 6-4, but Federer roared back in the second to take it 6-1.

However, with the momentum seeming to be with the 17-time Grand Slam champion, it was Nishikori who edged ahead when he broke to move 3-1 in the third.

And after comfortably holding serve in his next two service games, the 23-year-old broke again to seal a first career win over Federer.

"He was my idol actually, so to beat him, that was one of my goals for my tennis career," Nishikori told a press conference.

"That it happens on clay is amazing because, you know, it's not my really favourite surface.

"I feel good, of course. I wasn't really expecting this, it is not easy, 6-2 in the third, that's not easy against him."

Three-time champion Federer, who beat Nishikori in straight sets in their only other previous clash in Basel in 2011, admitted Nishikori was a deserving winner.

"I'm disappointed with my match. Today Nishikori played better and the best man won," said

Federer.

Rafael Nadal eased into the last eight with a 6-2, 6-3 win over Mikhail Youzhny and will next face either Tommy Haas of Germany or Spanish compatriot David Ferrer.

The 26-year-old Nadal now stands at 28-2 on the season as he looks to reach his seventh final since his comeback from a seven-month injury lay-off in February.

"Since I've been back I haven't had the security that I am in my perfect moment or that I can give myself definite goals," said Nadal.

"I just to have try and feel that I am getting better and better day after day.

"I have to have my feet on the ground. I've made it to the quarter-finals of Madrid, which, for me,

it's lovely to be able to say that today.

"I'll try to enjoy the quarter-final match tomorrow."

Andy Murray also progressed but had to come through a gruelling three hour battle with Gilles Simon before advancing 2-6, 6-4, 7-6(8-6) to set up a meeting with sixth seed Tomas Berdych who was victorious over Kevin Anderson 7-6 (7/5), 7-5.

It was one round too far for Novak Djokovic's conquerer Grigor Dimitrov though as he was beaten 3-6, 6-4, 6-1 by Stanislaw Wawrinka.

On the women's side, world number one Serena Williams eased into the last eight as she dismantled 13th seed Maria Kirilenko 6-3, 6-1 in just an hour and four minutes.

Williams didn't even face a break point during the match as she steamrollered the Russian, and now faces Spaniard Anabel Medina Garringues in the last eight.

Williams is unbeaten on clay in eight matches so far this season, but after a similarly positive start to last season on the clay was followed by a shocking loss in the first round of the French Open, she says she has learned not to get overconfident ahead of Paris.

"I think more than anything I learned not to become over-confident," she said.

"I think I was a little confident last year and I felt really good; this year I'm going to take every moment like it's my last."

World number two Maria Sharapova, who has yet to drop a set, also continued her stroll into the quarter-finals as she overcame Sabine Lisicki 6-2, 7-5.

The reigning French Open champion said she feels more comfortable than she ever has on clay.

"I think when you win a Grand Slam on a surface, it would be pretty mean of me to say that I'm not comfortable on the surface," she said.

"It took me many years to get to the level of where I am today. It certainly didn't happen overnight."