Mona Barthel of Germany rallied to upset Ana Ivanovic of Serbia 7-5, 7-6 (4) on Wednesday in the first round of the Porsche Grand Prix.
Ivanovic led 5-3 in the first set and held three set points on Barthel's serve. But the wild card saved two, then fired an ace to turn the match around.
Agkul Amanmuradova of Uzbekistan replaced the injured Daniela Hantuchova in the main draw and went on to upset another Slovak, Dominika Cibulkova, 6-2, 5-7, 6-3.
Fourth-seeded Agnieszka Radwanska of Poland cruised past qualifier Greta Arn of Hungary 6-3, 6-4 to reach the quarterfinals.