World number two Kim Clijsters needed three sets to overcome Marta Marrero in the second round of the German Open.
It was the Belgian's first WTA Tour match since injuring her left wrist in March, and she looked far from her best in a 6-3 2-6 6-4 win.
"I wasn't expecting to come back and play my best tennis straight away," said Clijsters, who is playing with her wrist heavily strapped.
Second seed Amelie Mauresmo needed just 50 minutes to ease past Gisela Dulko.
The Frenchwoman, who had a bye in the first round as one of the top eight seeds, completely outplayed her 19-year-old Argentine opponent in a 6-1 6-2 win.
Dulko, ranked 67th in the world, finally bowed out by netting a backhand on the second match point.
World number three Mauresmo won the title in Berlin in 2001.
Venus Williams beat Eleni Danilidou 7-5 6-3 to reach the last eight.
The American former world number one is chasing her third straight title in the build-up to the French Open.
Karolina Sprem overcame Meghann Shaugnessy 6-2 7-6 (7/3) and next faces Clijsters.
And Russian teenager Maria Sharapova advanced to the third round when Petra Mandula retired with a shoulder injury at 4-5 in the first set.