Brisbane: Serena Williams' Australian Open preparations took a major hit Wednesday when she injured her left ankle at the Brisbane International, laying on the court for several minutes while she received treatment.

Williams, playing her second singles match since September, was serving for the match with a 6-2, 5-3 lead against Serbia's Bojana Jovanovski on Wednesday when she twisted the ankle and crashed heavily to the court.

The 13-time Grand Slam winner lay near the baseline for several minutes while getting medical attention. She was helped to a courtside chair and had the ankle re-taped before resuming the second-round match and losing the next point to surrender a service break to Jovanovski.

Williams limped through the next game, wincing in pain after at least two points, before securing a 6-2, 6-4 win to advance to the Brisbane quarterfinals in her first trip Down Under since winning the 2010 Australian title. The 30-year-old Williams said she'd need tests to determine the extent of the injury, but was "just thinking positive."

"I'm anticipating it'll be OK," she said. "My initial thoughts, I'm always thinking I can play on, but at the same time I don't want to stress it out right now.

"I'm just going to play it by ear and see how I feel when I wake up in the morning."

She was due to meet Slovakia's Daniela Hantuchova in a quarterfinal on Thursday.

The Australian Open starts Jan. 16 in Melbourne. Williams, a five-time winner at Melbourne Park, missed the 2011 Australian Open while she was recovering from two operations on her foot and blood clots in her lungs that kept her sidelined for about a year after Wimbledon 2010.

She won two tournaments heading into the U.S. Open in August but, after losing the final to Australia's Sam Stosur, Williams didn't play another tournament last year due to injuries.

Williams said her first thought when she sprawled to the court near the baseline on Wednesday was "not again."

"That's what I felt," she said. "I was like, 'No way!'"

Williams usually wears a protective guard on her left ankle, but took it off during the second set because it was irritating another minor injury on her foot.

She said she started to feel improvement after having treatment and "as long as I was able to walk, it was a little better," but wouldn't risk further problems by playing with an injury.

"Health is always first for me. We'll see how it goes. I don't know any answers right now," Williams said of her prospects for being fit for the Australian Open.

Stosur is already out after losing 6-4, 6-2 to Iveta Benesova in the preceding match on center court, extending a run of never advancing beyond the second round at her home tournament.

It was the 28-year-old Benesova's fourth win over a top-10 player.

The No. 54-ranked Czech had never taken a set off Stosur in four previous matches but now finds herself in a quarterfinal against Australian Open champion Kim Clijsters.

"Hopefully it was just a bad day and I will bounce back next week and the week after," Stosur said of her Australian Open preparations. "I don't want to dwell on it.

"It's not the ideal start but I am not going to panic and think it's all lost."

Estonia's Kaia Kanepi beat seventh-seeded Anastasia Pavlyuchenkova of Russia 6-0, 6-3 in another women's match.

On the men's side, second-seeded Gilles Simon of France beat Australian teenager James Duckworth 6-3, 7-5 and sixth-seeded Radek Stepanek of Czech Republic had a 7-6 (3), 6-2 win over Finland's Jarkko Nieminen.