MELBOURNE, Australia --
A rematch of the women's 2011 final is already in place, with defending champion Kim Clijsters and China's Li Na both winning Friday night to set up a meeting in the fourth round.
Top-seeded Caroline Wozniacki has not dropped a set in her quest for a first Grand Slam title.
Wozniacki could face Clijsters in the quarterfinals. But before Clijsters gets that far, she will have to beat French Open winner Li.
Li advanced when Anabel Medina Garrigues had to retire with an ankle injury midway through the first set.
"It was really tough, because she tried to continue to play, so I don't know (if) it's like real or fake ... some players they do that," Li said. Then, "I saw she couldn't run and she started to cry. I have to say I am so sorry for her."
Clijsters eased past Daniela Hantuchova 6-3, 6-2 at Hisense Arena. Clijsters' only loss to Hantuchova in 11 matches came at Brisbane two weeks ago when she withdrew with a hip injury in the second set of their semifinal.
Azarenka, who defeated Li to win the Sydney International last week, has only lost eight games at Melbourne Park. She remains one of three women who can overtake Wozniacki for the top ranking at the Australian Open.
Azarenka was annoyed with herself for needing five match points to finish off Barthel, who was on a 10-match winning run in Australia after capturing her first title at the Hobart International last week as a qualifier.
"I've been playing in the end not brave enough to finish the match. ... I had to get a little," angry, Azarenka said.
Information from The Associated Press was used in this report.