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Marketa Vondrousova was forced to retire from a WTA Tour event in Berlin, causing doubt over her Wimbledon title defence.
The Czech, a surprise winner of her first grand slam title last summer, sustained a nasty fall behind the baseline during her second-round match against Anna Kalinskaya at the ecotrans Ladies Open.
Vondrousova, who was leading 5-3 at the time, got up gingerly, holding her right hip area, and took an off-court medical time-out.
She returned with heavy strapping and played two more games but lost both before shaking hands with Kalinskaya.
As the defending champion, Vondrousova is due to play her first-round match at the All England Club on Centre Court on July 2.
The Czech's predecessor, Elena Rybakina, made it through to the quarter-finals with a 6-4 7-5 victory over Veronika Kudermetova.
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