Top-seeded Roberta Vinci advanced to the second round of the clay-court tournament in Nuremberg by beating Czech qualifier Barbora Krejcikova 6-2, 2-6, 6-3 on Tuesday.
Vinci will next face Dutch qualifier Kiki Bertens.
Fifth-seeded Sabine Lisicki had fewer problems against Lara Arruabarrena, winning 6-3, 6-4, while Julia Goerges defeated Cristina Dinu of Romania 6-1, 6-2.
Second-seeded Laura Siegemund of Germany breezed past Marina Melnikova of Russia 6-1, 6-0.
Also in the first round, sixth-seeded Misaki Doi of Japan beat Antonia Lottner of Germany 6-3, 7-6 (8).
Third-seeded Annika Beck, No. 4 Lesia Tsurenko of Ukraine and No. 7 Anna-Lena Friedsam of Germany also advanced from their second-round matches.