SYDNEY (AFP) - Spain's world No. 3 Garbine Muguruza pulled out of the Sydney International tennis tournament hours after reaching the quarter-finals on Wednesday, putting her Australian Open chances in jeopardy.
She had battled a muscle problem to overcome Kiki Bertens a week after retiring from the Brisbane International with cramps.
Leading Australian Open contender Muguruza was ahead 2-1 in the opening set when she sought a medical time-out.
"Since the start I felt a little bit my adductor (muscle), and I already felt it in Brisbane, so I thought I was going to be much better but in fact it came back," she told reporters.
"I asked for a medical time-out to try and make it better. It worked."
Muguruza showed few ill-effects upon her return to the court, claiming six of the next eight games to take a commanding lead against the 32nd-ranked Dutchwoman.
But the Spanish top seed needed a tie-breaker to see off her opponent 6-3, 7-6 (8-6).
The reigning Wimbledon champion would have faced Daria Gavrilova, who beat fellow Australian Samantha Stosur 6-4, 6-2 for a spot in the final four.
"It's always difficult when you have the pain and you have to play," Muguruza said earlier.
"I never really get to play a tournament right before a Grand Slam, but I wanted to come to Sydney and play. I adapt a little bit my game to the circumstances, and I'm happy that I won.
"It was close. But I'm happy to play a match and to win, of course. That was the point to come to Sydney."
Poland's Agnieszka Radwanksa advanced to her fifth Sydney quarter-final with a straight-sets win over American qualifier Catherine Bellis 7-6 (7-4), 6-0.
She will play Italian qualifier Camila Giorgi, who eliminated two-time Wimbledon champion Petra Kvitova 7-6 (9-7), 6-2.
In the men's event, Spanish top seed Albert Ramos-Vinolas was knocked out by Italy's Paolo Lorenzi 6-3, 7-5.
The Spanish world No. 22 needed treatment for a leg problem early in the second set but continued playing, without success, as Lorenzi moved into the quarter-finals.
Lorenzi will play Russian qualifier Daniil Medvedev for a semi-final berth.
French pair Adrian Mannarino and Benoit Paire progressed to the last eight with victories on Wednesday.
Fifth seed Mannarino downed Lithuania's Ricardas Berankis 6-2, 6-1, while Paire needed three sets to get past Argentina's Leonardo Mayer 6-2, 3-6, 6-1.