Wimbledon champion Marketa Vondrousova retired from her match in Berlin because of an apparent leg injury less than two weeks before play begins at the All England Club.
Vondrousova was leading 5-3 in her second-round match against Anna Kalinskaya at the grass-court Ladies Open when she slipped behind the baseline and clutched her right leg.
The 24-year-old Czech player got up holding her right hip area and returned after a medical timeout with the upper part of her leg heavily strapped. She played two more games, losing both, and then stopped.
First-round play begins at Wimbledon on July 1.
Also Thursday, top-seeded Coco Gauff beat Ekaterina Alexandrova 7-6 (6), 6-2, and second-seeded Aryna Sabalenka defeated Daria Kasatkina 6-1, 6-4.
Elena Rybakina reached the quarterfinals with a 6-4, 7-5 victory over Veronika Kudermetova.
Ons Jabeur shook off a slow start to beat Linda Noskova 6-7 (5), 6-3, 6-4.
