Later on Friday, world No.3 Coco Gauff overcame a scare from fellow American Hailey Baptiste to scrape into the last 16 in three sets, teeing up a clash with 19th seed Karolina Muchova, who beat Magda Linette 6-1 6-1.
Canadian young gun Mboko, 19, had to overcome a stern test in Danish 14th seed Clara Tauson - including letting three match points slip in the second set - before prevailing 7-6 (7-5) 5-7 6-3 on John Cain Arena.
In the process, 17th seed Mboko, who won the Canadian Open Masters 1000 title last year and made the Adelaide International final, reached the fourth round at Melbourne Park - her best result at a slam.
"I think it was just self belief at the end," Mboko said.
"I had so many chances in the second set but I've got to give credit where it's due, she was playing incredible tennis so I just had to lock in, in the important moments.
"This is my first time here so I'm really happy to go through to the fourth round.
"You're in Australia, it's warm, it's not so warm back home, so it's nice to be here right now."
Mboko - one of five teenagers to reach the third round - said it would be "super cool" to face Sabalenka for the first time.
The world No.1 overcame a fierce challenge from Anastasia Potapova before her class won out in a 7-6 (7-4) 7-6 (9-7) victory on Rod Laver Arena.
Gauff, seventh seed Jasmine Paolini, eighth seed Mirra Andreeva and 12th seed Elina Svitolina are among the other big names in action on Friday.
Belarusian superstar Sabalenka, who is yet to drop a set this summer, had to grit her teeth and outfight Potapova - including saving four set points in the second set.
Sabalenka, 27, is determined to reclaim the Melbourne Park title after Madison Keys denied her a three-peat in last year's final.
After Sabalenka prevailed in the first set tiebreak, she quickly seized control of the second, claiming a 4-1 lead with a double-break.
But Potapova dug in and again took the set to a tiebreak.
Potapova raced away to earn three set points - but let them slip, before spurning a fourth and Sabalenka only needed one match point to seal victory.
"She played incredible tennis. I was always on the back foot," Sabalenka said.
"To be honest, there are days where you just have to be there, just have to fight and try your best to put the ball back on that side.
"I don't know what was the key. Even though I was emotionally all over the place, I was able to still fight for every point.
"I'm just super happy that I was able to get this win."
Gauff dropped the first set against Baptiste but it seemed to steel the French Open champion, who went on a rampage from there, claiming a 3-6 6-0 6-3 victory on Margaret Court Arena.
"Honestly I didn't change too much - I think I tried to get more first serves in," Gauff said of the turnaround.
"She played so well in the first sets, maybe a couple points go my way it could be a different outcome but I wasn't too upset.
"I just said 'if she plays like this the whole match and I can't raise my level, then great job to her' - but I was able to raise my level and I'm happy with how I mentally stayed calm through that.
"It's not often you play two players like Muchova and Hailey so I think I'll need to try to take what I did today and try to make some more adjustments to do better."
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