Caroline Wozniacki takes a knock on the wrist a week before the Australian Open kicks off. (Source: AP)

World number eight Caroline Wozniacki pulled out of her first match at the Sydney International with a wrist injury on Monday, a week before the start of the Australian Open.

The 24-year-old Dane, who lost in the final of the Auckland Classic last week, had already had her left wrist strapped when she was forced to retire from her first-round match against Barbora Zahlavova Strycova.

The fourth seed lost the first set 6-4 and had just saved break points to hold her first service game at the start of the second set, leaving Zahlavova Strycova to go through to a second round tie against Samantha Stosur.

Former U.S. Open champion Stosur had earlier progressed at her home event with a rain-disrupted 7-6(3) 5-7 6-3 victory over another Czech in Lucie Safarova.