Australia's Samantha Stosur was forced to withdraw from her Indian Wells quarter-final match against Angelique Kerber due to a right calf injury on Thursday.
Former US Open champion Stosur was seeded seventh and held a 2-0 career record over fourth-seeded German Kerber, who receives a walkover into the semi-finals where she'll face either world number one Victoria Azarenka or Caroline Wozniacki.
"I hurt my right calf muscle in the last game of my match against Mona Barthel when I was serving for the match, so I don't know if you can get any more unlucky than that," said Stosur.
"I think we only played another four points in that match. I felt something go in my calf and it was hurting a fair bit. Yesterday I took the day off practice and only did treatment, probably iced it about 10 times.
"This morning I thought I would give it a shot, and tried to go out and warm up, and after about five minutes I knew that there was no chance I could play, unfortunately."
The injury has also put a cloud over her participation in the Miami WTA event which takes place later in the month.
"I'll talk to the physios and the doctors and work out a good plan for how many days off I need to take off and go from there," said Stosur.
"It's all a bit up in the air at the moment because I've never been through this type of injury before, so it's a matter of wait and see, talking to the people who know and reassessing each day."