Top seed and defending champion Victoria Azarenka shrugged off a sore ankle to reach the Indian Wells quarter-finals on Tuesday with a 6-3, 6-1 victory over Urszula Radwanska.
Azarenka remained unbeaten in a 2013 season that has included an Australian Open triumph and a WTA title at Doha. She next faces either former world No. 1 Caroline Wozniacki of Denmark or Russian Nadia Petrova.
But the win over Radwanska, ranked 37th in the world, was tougher than the scoreline might suggest.
"I think it was pretty obvious that I wasn't feeling that well," said Azarenka, who had three double faults in dropping her serve in the fourth game of the opening set.
"My ankle was bothering me. It has been bothering me for a while, so it hasn't been really getting better.
"But on the bright side," she added, "I won the match."