Azarenka was booed late in the match, when she smashed a ball into the back of the court after another frustrating error. She screamed loudly after losing big points to the incredibly consistent Radwanska, punched her thigh and her racket and even slapped the court. Nothing worked to change her fortunes.
"I'm not happy with what I did today, but on the court I felt like I could have played a lot better," Azarenka said. "I can't take away what she's done today. She played amazing."
The diminutive Cibulkova, among the shortest women on the WTA tour at 5-foot-3, pounded Halep from the back of the court to progress to her first Grand Slam semifinal since the 2009 French Open.
It was her second win in five major quarterfinals and served as a harsh lesson for Halep, who was appearing in her first.
"I'm not so tall, but I'm intense on the court," Cibulkova said, "and I'm powerful."
Halep only won 10 points in the second set as Cibulkova relentlessly attacked.
No. 20-seeded Cibulkova said her experience in the quarterfinals was the biggest factor against Halep, as "I was ready today and I knew what to expect ... I was perfect."
With such a golden opportunity for one of the four to now break through and capture a major, the deciding factor in the semifinals may be who can best handle the pressure.
Fifth-seeded Radwanska had never been beyond the quarters in Melbourne until she chipped, lobbed and sliced Azarenka off the court in a remarkable display of shot-making on Wednesday.
Cibulkova has made just one Grand Slam semifinal before, while Bouchard is a only playing her fourth major -- she didn't even make it out of qualifying at last year's Australian Open.
"Of course, a couple seeded (players) are out. Doesn't mean it's going to be easier and you have a title right away," Radwanska said. "It's a bit more pressure. This is the semifinal of a Grand Slam."
Radwanska should know. The draw opened up similarly at Wimbledon last year when Williams and Sharapova were upset early and Azarenka pulled out with an injury, leaving the Polish player as the highest remaining seed and the favorite to capture her first major.
Radwanska, however, crumpled in the semifinals against Sabine Lisicki, blowing a 3-0 lead in the third set. She said it's natural to feel nervous in these situations.
"I think in the beginning of the match it's always a little bit tough, especially it's the first semifinal," she said. "But hopefully after few games I'm going to be myself and play my best tennis."
Radwanska faces Cibulkova in the semis -- a player she's beaten four times in five matches, including a 6-0, 6-0 drubbing in the Sydney International final last year.
Cibulkova knows she doesn't have a great record against Radwanska, but she takes inspiration from Wawrinka's upset of four-time men's champion Djokovic in the quarterfinals after 14 consecutive losses to the Serb.
"You just want to prove it to yourself that you can do it, and that's what (Wawrinka) did," Cibulkova said.
Li has the most experience of any of the semifinalists playing in the latter stages of slams, but she's also been susceptible to buckling under pressure.
Li was up a set in the finals here against Kim Clijsters in 2011 and Azarenka in 2013, only to falter both times. She also nervously wasted four match points in a fourth-round loss to Clijsters in 2012, breaking down in tears afterward.