Reigning Wimbledon champion Marketa Vondrousova retired injured from her second-round match in the Berlin grass-court event on Thursday against Anna Kalinskaya.
Vondrousova was leading 5-3 in the first set when she slipped on the first point of the ninth game.
The fifth-seeded Czech walked to her bench holding her right hip and received medical treatment. She returned but, after losing two games, retired with the set tied at 5-5.
Vondrousova has under two weeks to recover for her title defence at Wimbledon, which begins on July 1.
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Unseeded Russian Kalinskaya advanced to the quarterfinals where she will face either Belarusian second seed Aryna Sabalenka or another unseeded Russian, Daria Kasatkina.
Vondrousova’s predecessor as Wimbledon champion Elena Rybakina of Kazakhstan, the third seed, fought back from a break down in the second set to beat unseeded Russian Veronika Kudermetova 6-4, 7-5.
Top seed Coco Gauff saved three set points in the first set before beating Ekaterina Alexandrova, 7-6 (8/6), 6-2.
