SYDNEY - World number eight Caroline Wozniacki retired with a wrist injury in her opening match at the Sydney International on Monday, but is confident she will play in next week's Australian Open. The Danish star had several visits from the trainer before calling it quits after the second game of the second set after dropping the opening set to Czech Barbora Zahlavova Strycova.

Wozniacki shook her head and walked to the net to shake hands with Zahlavova Strycova and forfeited the match. Zahlavova Strycova will now meet Australia's Sam Stosur for a place in the quarter-finals. Wozniacki, who lost to Venus Williams in the final of the Auckland Classic on Saturday, said she withdrew to help her chances of recovering in time for the year's opening Grand Slam, which gets under way in Melbourne on Monday. "I felt it during a shot. I hit it against the wind and hit it late and I felt it in my wrist," she said.

"I've had it before so I know what it is. It was painful every time I had to hit a backhand, so I didn't want to do it worse before Melbourne. "I'm just going to try and get some treatment on it and try and get ready for next week." Wozniacki, who lost to Serena Williams in last year's US Open final, said she was confident she will take her place in Melbourne. "I still have a week to go, so hopefully it'll be fine. We'll see how it feels tomorrow. Hopefully it's going to feel better already tomorrow," she said. "I'm confident that I'll be fine to play in Melbourne."

Wozniacki said she was not concerned about a lack of matches because of the injury setback. "Definitely feel like I've had enough matches. I feel like I've had some good matches last week (in Auckland) and made it to the final," she said. Defending champion Tsvetana Pironkova reached the second round after eliminating Italian eighth seed Flavia Pennetta 6-3, 7-6 (7/4).

Bulgaria's Pironkova, who once again had to play qualifiers to reach the main draw, will next take on American Madison Keys. Stosur took over three hours to overcome the Czech Republic's world number 16 Lucie Safarova 7-6 (7/3), 5-7, 6-3 to end a run of six successive defeats for the 2011 US Open champion.

Last year's Australian Open finalist and seventh seed Dominika Cibulkova advanced to the second round with a 6-2, 6-2 win over French qualifier Kristina Mladenovic. Cibulkova, who lost to Li Na in last year's Australian Open final, will now face Australian Jarmila Gajdosova, whom ousted Germany's Andrea Petkovic 6-1, 7-6 (7/5).