Azarenka fights back to advance at Indian Wells

Azarenka remained unbeaten in 2013, having successfully defended her Australian Open title and her WTA Doha crown.

The 23-year-old from Belarus, currently ranked second in the world behind American Serena Williams, is vying to become the first woman to win back-to-back titles at Indian Wells since Martina Navratilova in 1990 and 1991.

But she showed far from dominant form in a scrappy first set against Flipkens, a 27-year-old ranked 31 in the world.

"I just wanted to go to sleep instead of playing tennis," Azarenka said of her first-set struggles, which saw her broken three times in the frame after taking a 2-0 lead.

A stuffy nose compounded her problems, and once she'd dealt with that, she said, she began to feel better.

"I just blew my nose, started breathing better and calmed down and started to see what I had to do," she said.

Nevertheless, after she'd held her serve to open the second set she and Flipkens exchanged breaks in the next four games before Azarenka earned the decisive break in the eighth.

She served it out with a love game and a demoralized Flipkens had no answer in the third.

Even though it wasn't her best, Azarenka said it was a gratifying victory, one that showed she's maturing as a player.

"I'm really happy that I find the ability to turn around my matches no matter what the circumstances are on the court," she said.

"That's definitely what excites me the most... To know when to take your opportunities, when to do things is definitely a learning experience. I'm glad I'm starting to master that."

Azarenka, who next faces unseeded Urszula Radwanska of Poland, led a parade of the top 10 seeds into the women's round of 16 scheduled for Tuesday.

Second-seeded Maria Sharapova, No. 3 Agnieszka Radwanska and fifth-seeded Petra Kvitova had advanced on Sunday.

No. 4 Angelique Kerber of German advanced on Monday with a 6-1, 7-6 (7/4) victory over Belgian Yanina Wickmayer.

Seventh-seeded Australian Sam Stosur, a former US Open champion, defeated China's Peng Shuai 6-3, 3-6, 6-2 and eighth-seeded Caroline Wozniacki breezed past Russian Elena Vesnina 6-2, 6-1.

Kerber had to dig deep in the second set but said words of encouragement from her coach when she trailed 4-1 helped her turn it around.

"He was coming to me and just reminding me of the game plan we had before the match and just telling me to focus on my game, play point by point and believe in my game," she said. "It helps me."