Fourth-seeded German Angelique Kerber was gifted a place in the last four at the BNP Paribas Open when Australian Samantha Stosur withdrew before their quarter-final match on Thursday with a calf injury.
Kerber will next meet either Australian Open champion Victoria Azarenka of Belarus or eighth-seeded Dane Caroline Wozniacki who were scheduled to play later in the day.
Stosur, the seventh seed, injured her right calf on Tuesday while serving for the match during her 4-6 6-2 6-3 victory over Germany's Mona Barthel in the fourth round.
"I don't know if you can get any more unlucky than that," Stosur said in a statement. "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.
"After about five minutes, I knew that there was no chance I could play unfortunately. I think this is only the second time I've ever pulled out of a match in my career."
The other semi-final in the elite WTA event at Indian Wells will be contested between second-seeded Russian Maria Sharapova and her compatriot Maria Kirilenko.
Sharapova, the 2006 champion here, advanced with a 7-6 6-2 victory over sixth-seeded Italian Sara Errani on Wednesday while Kirilenko booked her place in the last four by upsetting fifth-seeded Czech Petra Kvitova 4-6 6-4 6-3.