Second-seeded Andrea Petkovic reached the quarterfinals of the Strasbourg International by beating Zhang Shuai of China 6-1, 6-3 on Wednesday.
The German fended off two break points in the first set, and broke Zhang's serve twice in each set. She next faces fifth-seeded Maria Kirilenko of Russia.
Kirilenko lost her serve five times before defeating Laura Pous-Tio of Spain 6-3, 3-6, 7-6 (5).
Fourth-seeded Nadia Petrova of Russia also advanced, rallying to beat Alize Cornet of France 2-6, 6-2, 6-2. She will next face Daniela Hantuchova of Slovakia, who beat Mathilde Johansson of France 6-4, 6-2.
Also, Lucie Hradecka beat Stephanie Foretz Gacon 6-2, 6-4 and Mirjana Lucic defeated Jelena Dokic 6-2, 6-2.