NUREMBERG, Germany — Top-seeded Andrea Petkovic retired with an injury during her opening match at the Nuremberg Cup on Monday, while fellow Germans Angelique Kerber and Sabine Lisicki advanced to the second round at the clay-court tournament.
Petkovic retired when she was 5-0 down to Julia Putintseva of Kazakhstan with what appeared to be a right thigh problem.
Earlier, the second-seeded Kerber defeated Rebecca Peterson of Sweden 7-5, 6-4 and the third-seeded Lisicki defeated Silvia Soler-Espinosa of Spain 6-4, 7-5.
Kerber next faces the Czech Republic's Klara Koukalova, who defeated Germany's Annika Beck 6-4, 7-6 (6), while Lisicki plays Lara Arruabarrena for a place in the quarterfinals.