Top-ranked Amelie Mauresmo withdrew from the Zurich Open on Thursday because of a shoulder injury.
The 26-year-old Frenchwoman aggravated a right shoulder injury that caused her to pull out of the Porsche GP in Stuttgart two weeks ago.
Mauresmo beat Samantha Stosur 7-6 (4), 6-3 Wednesday to reach the quarter-finals, but felt pain in a different part of her right shoulder during the match.