Defending champion Kim Clijsters knocked Caroline Wozniacki out of the top world ranking by defeating the Dane 6-3, 7-6 (7-4) to set up an Australian Open semifinal against No. 3 seed Victoria Azarenka. Clijsters, the No. 11 seed from Belgium, overpowered Wozniacki from the baseline to extend her perfect record in quarterfinals at Melbourne Park to 7-0. Clijsters, who saved four match points in her fourth-round match againstLi Na of China, is seeking her fifth Grand Slam tennis title to start off what she has said probably will be her final season on the tour. “I had to work really hard for it,” Clijsters said in a televised court-side interview. “Caroline is a great fighter. I was happy to not have a three-setter because it’s so hot.”