Defending Wimbledon champion Marketa Vondrousova retired hurt from her second-round match against Anna Kalinskaya at the Berlin Ladies Open.
The world number 6 was up 5-3 and serving for the first set when she had a nasty fall on the baseline.
After off-court treatment, she returned heavily strapped up to play two games but retired with the set tied at 5-5.
The injury raises doubts about whether she will be able to defend her Wimbledon title, with less than two weeks to recover before the competition starts.
Vondrousova is scheduled to start her title defence with a first-round match at the All England Club on Centre Court on July 2.
The Czech was a surprise winner at Wimbledon last year, beating the Tunisian Ons Jabeur in the final to claim her first Grand Slam.
The 24-year-old became the first unseeded player to win the Wimbledon women’s singles title.
Berlin results
Eight of the world’s top 10 women are competing in Berlin, with only top-ranked Iga Swiatek and world number seven Jasmine Paolini not in the fray.
Russia’s Kalinskaya , who advanced to the next round when Vondrousova retired hurt, will now face world number three Aryna Sabalenka.
Sabalenka brushed aside Daria Kasatkina 6-1, 6-4.
Elsewhere on Thursday (June 20), 2022 Wimbledon champion Elena Rybakina beat Veronika Kudermetova 6-4, 7-5.
Rybakina will now face former world number 1 Victoria Azarenka in a bid to advance to her first grass-court semi-final since her Wimbledon triumph.
Meanwhile, Jabeur prevailed against Linda Noskova to set up a quarter-final match against Coco Gauff.
World number two Gauff beat Russia’s Ekaterina Alexandrova 7-6 (8-6) 6-2.
Gauff defeated Jabeur at the French Open earlier this month.
Gauff, 20, will make her Olympic debut in Paris after being named a member of the US women’s singles team.
The American missed the Tokyo Olympics in 2021 after testing positive for Covid-19.