Qualifier Kateryna Bondarenko of Ukraine rallied to upset 15th-ranked Flavia Pennetta of Italy 4-6, 6-2, 6-1 Tuesday at the Porsche Grand Prix.
Bondarenko next plays Venus Williams or Anna-Lena Groenefeld.
The WTA indoor tournament features eight of the top 10 female players, with only Ana Ivanovic and Maria Sharapova missing.
Another qualifier advanced when Tsvetana Pironkova beat teenager Alize Cornet 6-2, 6-1. The Bulgarian next faces third-seeded Dinara Safina.
Safina had a bye into the second round along with the other top three players in the tournament _ Serena Williams, Jelena Jankovic and Elena Dementieva.
Marion Bartoli of France advanced by defeating Dominika Cibulkova of Slovakia 6-3, 6-1, and Victoria Azarenka wasted a 5-2 lead before overcoming Agnes Szavay 7-5, 6-3.