By Mark Lamport-Stokes
INDIAN WELLS, California (Reuters) - Top seed Victoria Azarenka charged ominously into the fourth round of the Indian Wells WTA tournament on Sunday while third-seeded Petra Kvitova made an unexpected early exit.
Belarusian world number one Azarenka crushed Russian Svetlana Kuznetsova 6-1 6-2, improving her record to 19-0 this year, but Kvitova was ousted 2-6 6-2 6-3 by American teenager Christina McHale.
The pony-tailed Azarenka, who was taken to a third set tiebreak in her opening match against Germany's Mona Barthel, broke Kuznetsova three times in the first set and twice in the second to sweep through.
Serving for the match at 5-2, she went 40-15 up before double-faulting but then sealed the win on the next point when her opponent's backhand flew long.
"I'm really pleased with that," a smiling Azarenka told reporters after dispatching Kuznetsova in one hour. "We have practised quite a few times, and I know she's a great player.
"She has so much experience and she's been a grand slam winner, so I knew she was gonna be dangerous.
"I really had to step it up from my last match," she added, referring to her three-hour battle with Barthel. "I'm glad I could perform much better... and show some good tennis."
Kuznetsova, who won the 2004 U.S. Open and the 2009 French Open, had won four of their previous meetings but she was outplayed by the Belarusian on a sun-splashed afternoon in the California desert.
Azarenka, who clinched her first grand slam crown at the Australian Open in January, will next meet Germany's Julia Goerges, a 6-3 6-4 winner against Spaniard Anabel Medina Garrigues.
"Of course, when you play No. 1 in the world you have nothing to lose," the 23-year-old said. "She's a tough player, she's just recently won a first grand slam and hasn't lost so far a match this year.
"I will just try to focus on my game and play my game, and then I see how far it brings me. It's a tough challenge... but I will be ready for it."
Kvitova made a strong start against the 19-year-old McHale before errors began creeping into her game and she was bundled out of the tournament after a match lasting nearly two hours.
"She played very solid and she didn't have many mistakes," the Czech said. "She was moving very well, and she played a lot of shots to the back. My serve was not too good, too, so it was tough."
French Open champion Li Na beat fellow Chinese Zheng Jie 6-1 6-3, her first victory over her compatriot in five career meetings.
"We stay in the national teams so we practise every day and travel all of the time, so it's very tough. But I was so happy because it's the first time I beat her.
"The last meeting was six years ago, so six years can change many things," added Li, who is affectionately known as "Big Sister Na" and "Golden Flower" in China.
In other matches, fifth seed Agnieszka Radwanska of Poland eased past Italy's Flavia Pennetta 6-4 6-2 while Czech Klara Zakopalova was gifted a spot in the fourth round when Russian Vera Zvonareva became the latest victim of a viral infection affecting the tournament.
(Reporting by Mark Lamport-Stokes; Editing by John O'Brien)