Ivanovic beats Petkovic in Stuttgart
Ivanovic needed just 72 minutes to dispatch the 25-year-old Petkovic, who is struggling to regain her form after injuries.
The eighth-seeded Nadia Petrova of Russia avoided an upset by beating 21-year-old Dinah Pfizenmaier of Germany 7-6 (2), 6-4. Mirjana Lucic-Baroni of Croatia defeated another Russian, Elena Vesnina, 6-0, 6-4.
Sabine Lisicki will face Nastassja Burnett in the late match.