Hingis, the former top-ranked player and defending champion, is playing her first tournament since injuring her ankle last October as she prepares for the Australian Open.

``The most difficult thing for me was probably to believe in myself again, that you can get up there and just play the way you are supposed to -- and even better,'' Hingis said.

She will face fifth-ranked Kim Clijsters, a 7-6 (5), 6-2 winner over Belgian Fed Cup teammate Justine Henin.

Alexandra Stevenson, who produced the upset of the tournament Wednesday with a victory over Australian Open champion Jennifer Capriati, dropped a 6-4, 6-1 decision to fellow American Meghann Shaughnessy. Shaughnessy will face Serena Williams, who advanced Wednesday night with a victory over France's Amelie Maursemo.

In the men's draw, France's Nicolas Escude withdrew before his quarterfinal because of a groin injury, handing Argentina's Juan Ignacio Chela a place in the semifinals.

Escude's withdrawal caused a reshuffle in the program, with American Andy Roddick rescheduled to play his quarterfinal against South Korea's Lee Hyung-taik on center court later Thursday.

The winner of the that match will meet No. 2 seed Roger Federer of Switzerland, who beat former world No. 1 Marcelo Rios 6-7 (2), 7-6 (4), 6-3, in the semis.

Max Mirnyi of Belarus beat Julien Boutter of France 6-4, 6-2 in the first men's quafterfinal.