World number one Roger Federer shook off a determined challenge from Spanish wild card Feliciano Lopez to advance to the semi-finals of the Madrid Masters with a 7-6 6-4 win.

The Swiss holder converted on one break chance out of 11 against the cagey left-hander, who joined second seed Rafael Nadal in an exit as the lights went out for home hopes.

Federer had to play swashbuckling tennis to edge past Lopez, who took the one-hour-plus first set into a tiebreaker.

The top seed only managed to lift it with a return winner to claim the opener, then earned the long break of the contest for 5-4 in the second on a pass of the Spaniard

The Swiss will face off Saturday against Nicolas Kiefer after the unseeded German upset Chilean fifth seed Fernando Gonzalez 7-6 (5) 6-2.

Federer, bidding for his seventh season title, was relieved to go through.

"I couldn't break early on, I was starting to get a bit concerned," said the winner, now 57-6 on the season and 6-0 in the series.

"But I think I got the upper hand quite early, after five or six games. I was playing well from the baseline, but would have been nice to break.

"He served well and only game me one or two chances. He got frustrated midway through the second and gave me the free points I needed to finally break. Otherwise, it would have gone to another tiebreaker."

AFP