Defending champion Jennifer Capriati fought her way to a 2-6, 6-2, 6-4 second-round win over Slovakian Janette Husarova at the Family Circle Cup on Wednesday.
"It's been a while since I played, and it feels a little different to be on clay again.
"It takes a little adjusting and she [Husarova] is obviously a clay-court player, so she was getting a lot of balls back and kind of giving me no pace," said the reigning French Open champion.
World number one Capriati slipped 5-0 behind in the first set before tightening her game for the final two sets.
Third-seeded Serena Williams also struggled in her match but became the first player into the quarter-finals with a 7-6, 6-3 third round victory over Frenchwoman Nathalie Dechy.
Only five of the original 16 seeds remain in the draw - Capriati, Williams, second seed Monica Seles, seventh seed Sandrine Testud and 13th seed Amanda Coetzer.
Among the seeds losing in the second round on Wednesday were fourth seed Jelena Dokic, sixth seed Amelie Mauresmo, eighth seed Meghann Shaughnessy, 10th seed Arantxa Sanchez-Vicario and 11th seed Daniela Hantuchova.