Two days after saving four match points and spraining her left ankle in a fourth-round win over French Open champion Li Na, Clijsters showed no signs of weakness as she continued her title defense at Melbourne Park with a 6-3, 7-6 (4) quarterfinal win over Wozniacki.
Wozniacki needed to reach the semifinals to retain the top ranking she has held at the end of the previous two seasons. Her place in the rankings has attracted some criticism because the 21-year-old Dane has never won a major.
But even after another major setback, Wozniacki remained confident she will not only reclaim the top ranking but will get her Grand Slam breakthrough.
"You know, I will get it back eventually, so I'm not worried," she said. Critics "talk to me like I'm finishing my career and I only have one year left and time is running out.
"The fact is I still have quite a few good years in front of me."
Clijsters slipped to No. 14 after beating Li in the last Australian final, losing in the second round at the French Open and then missing the next two majors due to injuries. But after losing her first four finals in the majors, she's learned how to win them.
She set an example for Wozniacki of how to go about it.
Both players started nervously Tuesday, with three service breaks until Clijsters held in the fourth game. The 28-year-old Belgian dictated play from her first hold until she was serving for the match while a break up in the second.
She had the rally on her racket at 30-30 but let her guard down and allowed Wozniacki back into the match. Wozniacki took a chances and got back level, going into the tiebreaker with momentum.
Clijsters had never lost any of her eight previous tiebreakers at Melbourne Park, and she hit a backhand down the line to take a 5-4 lead. She set up double match point with a cross-court forehand winner and sealed it with a volley.
"It definitely didn't feel like being up a set and 5-2," Clijsters said. "I had to work really hard for it. Caroline is a great fighter.
"I was happy to get through, and not in a three-setter because it's so hot," she said.
The crowd at Rod Laver Arena was solidly behind Clijsters from the start, shouting, "C'mon Kimmie," in between nearly every point and cheering when Wozniacki missed a shot.
Azarenka opened the action on Rod Laver in a match that contained 15 breaks of serve, including eight in the first set.
After being comprehensively outplayed in the opening tiebreaker, Azarenka won seven straight games to move closer to the victory that kept her among the three players who can overhaul Wozniacki at No. 1.
The 22-year-old Belarusian, who makes a distinctive hooting sounds as she hits the ball, extended her winning streak this season to 10 matches, including a title at Sydney, where she beat Radwanska in the semifinals. She served six double faults and had 38 unforced errors but showed maturing mental resolve by holding her nerve on the big points.
"I'm really happy with my win. I think it was very important to see how I could adjust after not playing really well in the first set," she said. "I completely turned it around.
"Today I really tried to forget about the first set and start from zero and really fight hard. So I think that was a different mental approach a little bit."
In the remaining women's quarterfinals Wednesday, Sharapova plays Ekaterina Makarova, who beat five-time champion Serena Williams in the fourth round, and No. 2 Kvitova takes on unseeded Sara Errani of Italy.
Information from The Associated Press was used in this report.