Serena Williams, Maria Sharapova coast

MELBOURNE, Australia -- Serena Williams was only two points from her 500th career match win when she tumbled to the court in the second round of the Australian Open.

It's OK, she thought, it's the good ankle. After sitting and watching Barbora Zahlavova Strycova's shot float out to end the penultimate rally, Williams got up and whipped a backhand winner down the line to move into the third round with a 6-0, 6-4 victory Thursday.

It improved her career record to 500-104 in tour matches and it was her 16th consecutive match win at Melbourne Park, where she has won five of her 13 Grand Slam titles. Her older sister, Venus, has a win-loss record of 589-147 but is missing the Australian Open to recover from illness.

"It's totally fine. It was my good ankle, so I'm good," she said, playing down concern that the fall had aggravated the left ankle sprain that had hampered her preparation for the season's first major. "There was no extra pain. I twisted it. But it's all taped up, so the tape really, really helped."

She'd earlier put it down to just having "wobbly ankles."

"I wasn't meant to be a ballerina or anything," she told a post-match TV interview.

"I knew I had to get there, too, because I do everything she does," Williams said. "It's great, it's like the ultimate."

Not quite.

"The first thing I asked, of course, 'Is there anyone that achieved a thousand?' "

There's been two: Martina Navratilova had a career record 1,442-219, and Chris Evert retired with a 1,309-146 record.

"I never will get there, either, but it's really cool," Williams said. "Five hundred is a lot of matches to play, let alone to win."

Williams won the Australian Open in 2009 and 2010 but didn't get to defend her title in 2011 because she was injured.

With top-seeded Caroline Wozniacki on an off-day, No. 2 Petra Kvitova moved into the third round with a 6-2, 2-6, 6-4 win over Carla Suarez-Navarro. Kvitova, who lost in the first round at the U.S. Open in the first major after winning Wimbledon, was down a service break in the third before recovering to beat the Spaniard.

"In the beginning it was OK, but I made many, many, many mistakes," Kvitova said of her 48 unforced errors. "It's part of my game but it's too many. It was very tough to get back in the third set."

Maria Sharapova, one of the three former champions in the women's draw, reached the third round after just two hours on court in two matches.

The 2008 champion had a 6-0, 6-1 second-round win over U.S. qualifier Jamie Hampton in 64 minutes.

Sharapova did not play in any warmup events and spent nearly two weeks in Melbourne ahead of the season's first major while she rested an injured left ankle.

"It was more about getting my feet going ... worrying about myself," Sharapova said. "Yeah, started my preparations in the offseason a little late, took a bit of extra time in practice instead of rushing into a tournament."

She'll meet No. 30 Angelique Kerber, who beat Canada's Stephanie Dubois 7-5, 6-1.

Seventh-seeded Vera Zvonareva, a two-time semifinalist at Melbourne Park, had a 6-1, 7-6 (3) over Lucie Hradecka. No. 21 Ana Ivanovic also advanced, beating Dutch player Michaella Krajicek 6-2, 6-3.

Ninth-seeded Marion Bartoli beat local hope and former quarterfinalist Jelena Dokic 6-3, 6-3 and No. 27 Maria Kirilenko of Russia topped Aleksandra Wozniak of Canada 6-4, 1-6, 6-2. Dokic double-faulted on break point in the seventh game of the second set, then Bartoli closed with ace.

Three seeded players were beaten: No. 23 Roberta Vinci lost to China's Zheng Jie, No. 29 Nadia Petrova fell to Sara Errani and No. 25 Kaia Kanepi lost to Ekaterina Makarova.

Defending champion Kim Clijsters is into the third round on the other half of the draw and advanced on Wednesday along with top-ranked Caroline Wozniacki, No. 3 Victoria Azarenka and former No. 1-ranked Jelena Jankovic.

Clijsters will next face longtime friend Daniela Hantuchova in the third round, and a win there could set up a fourth-round match against French Open champion Li Na, a rematch of the 2011 Australian final.