The women's draw for the Australian Open is resembling the march of the walking wounded, with more than a quarter of the top 25 ruled out or carrying injuries into the year's first Grand Slam.

Top seed Caroline Wozniacki joined the long list of injured players when she strained her left wrist in her quarter-final defeat to Pole Agnieszka Radwanska at the Sydney International late on Wednesday.

While a scan on Thursday cleared the Dane of major damage, she is racing against time to prove her fitness before the tournament starts on Monday.

"She is very hopeful of being able to compete at the Australian Open and will do everything she can to be ready," tournament organisers said of Wozniacki on Thursday.

Injuries have already robbed the tournament of two major drawcards in seven-times Grand Slam champion Venus Williams (illness) and German world number 10 Andrea Petkovic (back).

Several other headliners, including Kim Clijsters and Serena Williams, go into the tournament with injury concerns.

Defending champion Clijsters pulled out of the warm-up Brisbane International after suffering a hip muscle injury, while five-time winner Williams twisted an ankle at the same tournament.

Williams, who is well short of match practice, said she was feeling as fit as she ever had but could not give her ankle a clean bill of health just four days before the tournament starts.

"The ankle is better. I'm taking it a day at a time," Williams, whose last tournament prior to Brisbane was at the US Open in September, told reporters.

"It's not 100 percent, but it's better than it was last week and that's always a step forward."

Three-times Grand Slam champion Maria Sharapova was forced to pull out of Brisbane with an ankle injury, while 20th-ranked Italian Flavia Pennetta retired hurt with a back injury in the final of the Auckland Classic against China's Zheng Jie on Sunday.

The raft of injuries may be a headache for organisers, but had left the field wide open for a dark horse to gallop to the title, according to former Wimbledon champion and TV pundit Pat Cash.

"Tennis is a brutal sport. You can be fit as hell doing gym work and running but once you get on the tennis court and start playing matches, it's tough," the Australian said.

Cash has pinpointed world number two Petra Kvitova as a good bet to seal her second Grand Slam trophy after the Czech continued to improve after storming to the Wimbledon title last year.

"She is probably going to be the only player around the mark going in with real form and confidence," he added.