Sydney, Jan 11 (Agencies): World number one tennis star Caroline Wozniacki was knocked out in the second round of the Sydney International in straight sets on Tuesday.

Denmark's Wozniacki, who had a bye into the second round, was beaten by Slovakia's 32nd-ranked Dominika Cibulkova, 6-3, 6-3, in one hour 40 minutes of a rain-interrupted match.

It was Wozniacki's first loss to a player ranked outside the WTA top 30 since losing to Petra Kvitova in the semi-finals at last year's Wimbledon.

Wozniacki goes into next week's Australian Open in Melbourne under growing pressure to win her first Grand Slam after winning 12 WTA singles titles last year and hitting number one in the rankings last October.

It was Wozniacki's first WTA match of the new season after she played in a Hong Kong exhibition last week.

Wozniacki has a poor record in Sydney, reaching the quarter-finals on her debut in 2009 and losing in the first round to China's Li Na last year.