World No 1 Caroline Wozniacki shrugged off defeat in her first competitive match of the year at the Sydney International on Tuesday, saying she would be ready to go at the Australian Open next week.

Dane Wozniacki went down 6-3, 6-3 to Slovakia's Dominika Cibulova in a rain-disrupted second-round match and was later joined at the exit by second seed Vera Zvonareva and fourth seed Sam Stosur.

"It happens," the 20-year-old said. "Sometimes you win, sometimes you lose. You need to learn from the losses.

"It's the first tournament of the year. I just want to get the match playing going. There were a few positive things in there that I can take out of it, and then I just need to work on the rest. But I'm confident that for Melbourne I'll be okay."

Russian Zvonareva, the world No 2, also departed early with her 7-5, 7-5 loss to Italy's Flavia Pennetta, crumbling after fighting her way back into the match in the second set.

Stosur, the best hope of a local champion at Melbourne Park, made it a trio of upsets when she was beaten 3-6, 6-3, 6-4 by twice Grand Slam champion Svetlana Kuznetsova in a sloppy match, the Russian edging the unforced error count 41-39.

World No 3 Kim Clijsters had no such problems in her second-round match, clinically dispatching frustrated Czech Barbora Zahlavova Strycova 6-1, 6-4 to reach the quarter finals.

Clijsters, who dropped just three games in the first round, wrapped up the first set with a minimum of fuss before coming through a ding-dong second set that featured five service breaks.

"I feel that I'm really getting into a groove from the beginning of the match," said the 27-year-old, who will meet seventh seed Victoria Azarenka in the last eight.

"I think that's an important feeling to have, knowing that you can start off well and really kind of build from there."

Clijsters ignored Zahlavova Strycova's racquet-smashing histrionics in the second set - "I hear it, but I'm focused on the next point" - and declared herself in tip-top condition for the year's first

Grand Slam next week in Melbourne.

"I feel good, I feel fit," said the US Open champion. "I think that's obviously something that adds a lot to your confidence if you feel good out there.

"You have no small problems or you don't feel that physically you're struggling with any injury, you feel fine."

Zvonareva, runner up to Clijsters at Flushing Meadows and to Serena Williams at Wimbledon last year, had arrived in Australia full of confidence after an excellent 2010, but that lasted just 100 minutes at the Sydney Olympic Centre.