Top-ranked Ash Barty withdrew from the French Open during her second-round match on Thursday because of an injury.
The 2019 champion trailed 6-1, 2-2 when she returned to her chair and signalled she was not able to continue against Polish rival Magda Linette on Court Philippe Chatrier.
The Australian started the match with her left thigh bandaged and it was immediately clear she could not move properly. Too slow to chase her opponent's shots, she suffered in long rallies and struggled with her first serve.
Barty had called for a medical timeout at the end of the opening set.
Dealing with a left hip problem, Barty had struggled through a 6-4, 3-6, 6-2 win against 70th-ranked American Bernarda Pera in the first round. She said afterward she was not fully healthy and would adopt a one-match-at-a-time approach.
Barty decided not to defend her title last year because of the coronavirus pandemic, choosing instead to remain home in Australia.
In the build-up to this French Open, she played 13 matches on clay, winning 11. But she was forced to retire in the quarterfinals in Rome in May because of an injury to her right arm.