Sabalenka, 26, cantered through the first set of her match against Anastasia Pavlyuchenkova at Rod Laver Arena on Tuesday night.
But Pavlyuchenkova hit back to claim the second set - the first Sabalenka has lost at Melbourne Park since the 2023 final against Elena Rybakina - and force the match to a decider.
A shaky Sabalenka managed to hold her nerve to prevail 6-2 2-6 6-3 in an hour and 53 minutes and tee up a semi-final against 11th seed Paula Badosa, who upset third seed Coco Gauff 7-5 6-4 earlier on Tuesday.
"I was all over the place," Sabalenka said after her 19th consecutive win at Melbourne Park, as she attempts to become the first woman since Martina Hingis (1997-1999) to win three titles on the spin.
Aryna Sabalenka toughed it out in her win over Anastasia Pavlyuchenkova. (Lukas Coch/AAP PHOTOS)
"I'm really glad that at some point I was able to put myself back together, and I was able to, you know, like, I don't know, just get back to the match.Â
"I was able to keep fighting, keep trying, and I was able to turn around this match."
Sabalenka was particularly pleased with how she handled a tricky wind that bothered both players.
"I was just, like, trying to figure out how to play in these conditions. I was struggling a lot with, like, finding my rhythm, finding the solution in these conditions," she said.
"It's not about being scared. It's about finding the way out ... Yeah, I'm happy that I was able to do that."
ğ�Ÿğ�Ÿµ-ğ�Ÿ¬ at Melbourne Park ğŸ˜�— #AusOpen (@AustralianOpen) Aryna Sabalenka's title defence is STILL ALIVE as she battles past Pavlyuchenkova's challenge 6-2 2-6 6-3. #AusOpen • #AO2025 pic.twitter.com/AyJnkxpyo8January 21, 2025
Sabalenka took 31 minutes to wrap up the first set, letting out a "let's go" and fist pumping after breaking Pavlyuchenkova to seal it.
But 27th seed Pavlyuchenkova, 33, wouldn't lie down.
Instead she broke the Belarusian and went toe-to-toe with Sabalenka from the baseline in the second set.
Anastasia Pavlyuchenkova was gallant in her three-set loss to Sabalenka. (Joel Carrett/AAP PHOTOS)
Pavlyuchenkova raced to a double break and 4-1 lead, then a 5-2 lead before serving out the set.
The pair twice traded breaks in the decider before Sabalenka seized control.
The Belarusian broke Pavlyuchenkova at 4-3 then rediscovered her ruthless edge to serve out the match.
It brought to an end Pavlyuchenkova's impressive run to a fourth Open quarter-final.
"Here I felt like I was playing really good tennis," said Pavlyuchenkova.
"Even today, parts of the match I felt like, yeah, I was hitting the ball well, and I could compete with world No.1.
"So that was my feeling."
