Caroline Wozniacki recovered from a shaky opening set to battle past Swede Sofia Arvidsson 3-6, 7-5, 6-2 in the third round of the Indian Wells WTA tournament on Monday.
The defending champion, who beat Frenchwoman Marion Bartoli in last year's final, initially struggled to hold serve on a cool evening but found her form to break her opponent three times in the final set and seal victory in two hours, 37 minutes.
The 21-year-old Dane pumped her left fist in delight after pouncing on a drop shot and unleashing a crosscourt backhand winner to break the Swede and lead 5-2.
The fourth seed then coolly served out for victory, ending the match with a forehand winner after Arvidsson had again teased her forward with a drop shot.
"I knew it was going to be a tough match," Wozniacki said. "I've known Sophia since I was 12 or 13 and we know each other's games so well.
"She just came out from a win in Memphis and I knew she was on fire. I'm so happy with this win," added the Dane, who will next play Ana Ivanovic, after the Serbian was a 6-7, 6-3, 6-2 winner against Kazakhstan's Ksenia Pervak.
While Wozniacki stayed on track to defend her crown, Samantha Stosur, the US Open champion, exited the competition.
The sixth seed lost to the Russian Nadia Petrova 6-1, 6-7, 7-6.
Novak Djokovic cruised through to the fourth round in the men's competition at Indian Wells with a 6-2, 6-3 success against South Africa's Kevin Anderson.
But it was not such good for the American men.
Mardy Fish was the highest men's seed to fall as the eighth seed was beaten 6-3, 6-4 by Matthew Ebden, the Australian, while Andy Roddick, the 2003 US Open champion, went down 6-3, 4-6, 6-2 to Tomas Berdych, the seventh seed.