Australian Open champion Caroline Wozniacki has pulled out of the Citi Open because of an injured right leg.

The hard-court tournament announced the No. 1-seeded Wozniacki's withdrawal Tuesday, hours before she was to face qualifier Anhelina Kalinina of Ukraine.

Wozniacki was replaced in the field by Ysaline Bonaventure, who lost in qualifying.

After practicing on-site Monday, Wozniacki said her leg is "just something that has been nagging a little bit, but hopefully it'll be fine."

She won her first Grand Slam title in January at Melbourne to return to No. 1 in the rankings. She is currently No. 2.

Wozniacki hasn't played a match since losing in the second round at Wimbledon on July 4. She now has less than a month to get ready for the U.S. Open, which starts on Aug. 27.