Kim Clijsters edged closer to the world number one spot with a comfortable victory to reach the quarter-finals of the Filderstadt Grand Prix in Germany.
Clijsters, who who could replace Maria Sharapova at the top of the rankings this week, beat Karolina Sprem 6-3 6-2.
Nadia Petrova and Amelie Mauresmo had easy wins over flu-stricken opponents.
Sixth-seeded Petrova beat fellow Russian Elena Likhovtseva 6-1 6-1 while Mauresmo was 6-0 up when Jelena Jankovic retired early in the second.
Clijsters needed six break points to establish a 2-0 lead at the start of the match but Sprem immediately broke back.
The Belgian then needed another six break points before breaking again for 4-2.
The pair exchanged breaks at the opening of the second set, before Clijsters won four games in a row to build a 5-1 lead and set up a meeting with fifth seed Elena Dementieva.
Likhovtseva missed an early chance to break and then had to leave the court during the opening set to be evaluated after having her blood pressure taken.
Jankovic, who also called for the doctor after dropping the first set, looked pale but did occasionally produce a competitive rally.
Mauresmo, though, was in superb form, sometimes serve-volleying and constantly causing damage with her trademark backhand.