Spain's world number three Garbine Muguruza was forced out of the Sydney International with an injury following her win over Kiki Bertens on Wednesday.
A week after retiring from the Brisbane International with cramps, leading Australian Open contender Muguruza had an early medical timeout for a thigh injury before beating Bertens 6-3, 7-6 (8/6).
But the win came at a cost. The Wimbledon champion later announced she would be pulling out of the tournament, handing Australian Daria Gavrilova direct passage to the semi-finals.
Muguruza's decision comes less than a week out from the Australian Open in Melbourne.
"I am disappointed but I have talked to the WTA doctors and my team after the match today and following their recommendation, I have to withdraw from the tournament," Muguruza said.
"I have felt pain in my right adductor since I started practising here.
"Yesterday I felt better and wanted to play. However, during the match today the pain has been there all the time but I wanted to compete."
Muguruza was leading 2-1 in the opening set when she sought a medical time-out.
She showed few ill-effects upon her return to the court, reeling off six of the next eight games to take a commanding lead against the 32nd-ranked Dutchwoman.
The Spanish top seed claimed the first set before needing a tiebreaker to see off her opponent.
Gavrilova downed Samantha Stosur in their all-Australian second round night match 6-4, 6-2 and will benefit from Muguruza's setback to advance to the last four.
Poland's Agnieszka Radwanska reached her fifth Sydney quarter-final with a straight-sets win over American qualifier Catherine Bellis 7-6 (7/4), 6-0.
Radwanska will play Italian qualifier Camila Giorgi, who eliminated two-time Wimbledon champion Petra Kvitova 7-6 (9/7), 6-2.