(CNN) -- Petra Kvitova is just two wins away from moving to the top of the women's tennis rankings, after current world No. 1 Caroline Wozniacki suffered a quarterfinal defeat at the Sydney International on Wednesday.
Dane Wozniacki served for the match against Poland's Agnieszka Radwanska, but slipped to a 3-6 7-5 6-2 defeat.
Second seed Kvitova knows victory in Sydney will see her claim the number one spot for the first time in her career ahead of next week's Australian Open.
And the 2011 Wimbledon champion remains on course to achieve that landmark after beating Slovakia's Daniela Hantuchova 6-0 6-4.
Wozniacki first rose to the summit in October 2010, but, unlike her fellow 21-year-old Kvitova, she is yet to claim a first grand slam title.
Defending champion Li Na will be Kvitova's next opponent, after the fourth seed beat Lucie Safarova of the Czech Republic 6-2 7-6.
Radwanska's reward for defeating Wozniacki is a clash with third seed Victoria Azarenka, after the Belarusian's 7-5 6-4 success over eighth-seeded Frenchwoman Marion Bartoli.
Meanwhile, German Andrea Petkovic, who was beaten by Radwanska in the first round on Tuesday, has been forced to withdraw from next week's Melbourne grand slam with a back injury.
Petkovic, a quarterfinalist at last year's Australian Open, had been seeded 10th ahead of the first round draw, but used her official Twitter account to announce she would not be taking part in the tournament.
"Sorry to announce that I had to withdraw from the Australian Open with a lower back stress fracture," she said. "Going back home, will miss my Aussie fans!"
Meanwhile in Tasmania, Spanish second seed Anabel Medina Garrigues suffered a shock defeat to German qualifier Mona Barthel in the second round of the Hobart International.
The 21-year-old Barthel earned a quarterfinal against defending champion and fifth seed Jarmila Gajdosova.
Australian Gajdosova, born in Slovakia, battled to a 6-3 1-6 6-4 victory against her Russian-born Fed Cup teammate Anastasia Rodionova.
Another seed to progress was Israel's Shahar Peer. The sixth seed beat Sacha Jones, a New Zealand-born 21-year-old who recently decided to switch her allegiances to Australia, 7-6 6-4.