The Australian Open will have a new women's champion after Victoria Azarenka joined the purge of the favourites in Melbourne.
After fourth-round exits for Serena Williams and Maria Sharapova, Azarenka was toppled by a superb display of artistry from Agnieszka Radwanska.
The Pole played the role of Stanislas Wawrinka, who on Tuesday night ended three-time defending champion Novak Djokovic's 25-match winning streak at Melbourne Park.
Azarenka had not lost at the tournament since 2011, a stretch of 18 matches, but she suffered the indignity of a love set as Radwanska pulled off a 6-1 5-7 6-0 victory.
It is the first time in the Open era that both defending champions have lost in the quarter-finals at the Australian Open.
The women's champion will come from two-time finalist Li Na, 19-year-old Eugenie Bouchard, Radwanska and Slovakia's Dominika Cibulkova, who defeated Simona Halep on Wednesday morning.
Radwanska had only previously made the last four of a grand slam at Wimbledon, where she was beaten by Williams in the final in 2012 and Sabine Lisicki in the semi-finals last year.
She went into Wednesday's match on a seven-match losing streak against Azarenka, who had also won their last 12 sets dating back to a quarter-final meeting here two years ago.
But she was simply outplayed by Radwanska, whose touch and range of shots is unique at the top of the women's game.
Azarenka managed to scrap her way into a decider but there Radwanska was sublime, drawing gasps from the crowd with some of her winners.
The fifth seed said: "There were a lot of good rallies, amazing points. I was really feeling good on the court today. I was feeling I could really do everything.
"This is for sure one of my greatest matches at the slams, especially here. I made a couple of times the quarter-finals. A few times I was pretty close, even against her a few years ago. She's played great tennis here.
"I'm so happy and pleased, especially that I beat one of the best players in the world. It was not an easy draw, not an easy quarter-final. I'm very happy that I made my first semi-final here."
Radwanska will be a big favourite to beat Cibulkova and reach the final, but she will remember only too well the strange events of Wimbledon last year.
Then the Pole was by far the highest seed left in the semi-finals only to lose to Lisicki.
Radwanska said: "Of course, a couple of seeds are out but it doesn't mean it's going to be easier and you have a title right away. It means that other players are playing great tennis this week."
Azarenka struggled to hide her frustration throughout the match but she was magnanimous in defeat.
The second seed said: "She was aggressive. She was making everything. She was guessing right. I was just playing a little bit too predictable.
"In the second set I managed to fight back. The third set, the first game was important. I let it go easily. From there I just couldn't get back to it.
"She was just doing everything a little bit better than me. I was just watching. I was like a spectator a little bit."
The 24-year-old insisted it would not take long to get over the disappointment, saying: "You can look at it as a lost opportunity but there's nothing else I can do right now.
"What I have to think is what I have to do better next time. If I wouldn't be able to do much better than today, it's better to just stop playing tennis. But I know that I can do better."
Cibulkova is through to her second grand slam semi-final having previously made the last four at the French Open in 2009 as a 19-year-old.
The 20th seed maintained the form she showed in knocking out Sharapova to thrash an out-of-sorts Halep 6-3 6-0.
Radwanska has won five of their six previous meetings but Cibulkova did get the better of the Pole in the final of the WTA Tour event in Stanford last year.
She said: "Many times before at the big tournaments I beat top-10 players, then you have to play against somebody you should beat and it's a completely different story.
"It's going to be very tough (against Radwanska). It just gives me confidence to go into this match and to know that I've beaten her."