MELBOURNE, Australia - Caroline Wozniacki and Li Na became the first two players into the quarterfinals of the Australian Open, both winning in straight sets on a sunny Sunday afternoon in Melbourne.

World No.1 Wozniacki was the first to move through, starting slowly - she lost three of the first four games - but settling in nicely for a 63 64 victory against Anastasija Sevastova, who was playing her first Grand Slam second week.

"She was playing pretty flat and deep with her forehand, then she was spinning it up quite a bit with her backhand. It was tough to get a rhythm," Wozniacki said. "I'm happy I was able to fight and get a lot of balls back and get through."

Next up for Wozniacki is either No.6 seed Francesca Schiavone or No.23 seed Svetlana Kuznetsova, who played their fourth round match later.

Also moving into the quarterfinals was No.9 seed Li Na, who fired 27 winners - including 13 off of her deadly forehand wing - to pull off a minor upset over No.8 seed Victoria Azarenka, 63 63. Both Li and Azarenka had lost to Serena Williams here a year ago, Azarenka in the quarterfinals and Li in the semis.

"This is a dream for me. Until now I've just been following the dream," Li said. "Last year I needed two more steps. Hopefully this year I can do better."

Next for Li is either No.14 seed Maria Sharapova or No.30 seed Andrea Petkovic, who played in the night session on Rod Laver Arena.