Wimbledon champion Roger Federer was given a walkover into the semi-finals of the Swiss Open on Friday when his opponent David Sanchez of Spain pulled out with a knee injury.

To the dismay of local fans keen to see their compatriot extend his run of 14 match wins dating back to April 4, the popular 21-year-old was given a welcome rest that boosted his hopes of winning his home title for the first time.

Unseeded Sanchez, 25, who beat defending champion and fellow-Spaniard Alex Corretja in the second round, withdrew suffering from tendinitis in his left knee.

His exit, on a hot day in the Swiss Alpine resort village, means that the in-form Federer, who heads the ATP Champions Race will meet either last year's beaten finalist Argentine Gaston Gaudio, seeded four, or unseeded Austrian Stefan Koubek in the semi-finals.

The organisers promptly organised a 20-minute exhibition game to please the crowd with Federer playing against compatriot Michael Lammer.

If Federer continues his current winning form he will meet a Czech Republic player in the final, the second semi-final having been decided earlier when compatriots Radek Stepahek and Jiri Novak succeeded in their respective quarter-finals.

Eighth seed Stepanek beat second-seeded German Rainer Schuettler, the beaten finalist in this year's Australian Open, 6-4 6-2 after third seed Novak had seen off the challenge of fifth seed Juan Ignacio Chela of Argentina 6-3 6-3.

Novak's victory was his first in three meetings with Chela and prompted him to suggest he had rediscovered his best form. But, he warned, that was not likely to be any assurance of an easy passage against Stepanek.

"We are friends and we play a lot together in practice," said Novak. "He has improved a lot this year and he has nothing to lose. Our rankings will mean nothing in this game."