The Belarusian swept past 32nd-ranked Belgian Elise Mertens 6-2, 6-3 on Margaret Court Arena to burgeon her growing status as a favourite for the first Grand Slam of the year.
Sabalenka needed just 74 minutes to beat her former doubles partner -- the pair won five titles together including the Australian Open in 2021 -- but said it hadn't been as easy as it looked.
"It's really tough to play against her, especially. She's a great player, unbelievable fighter," said the powerful Sabalenka, who is yet to win a major.
"I knew it's going to be tough. I'm super happy that I was able to stay focused from beginning to the end to win this match because she's an amazing player."
Runner-up at the WTA Finals last year, Sabalenka has apologised for unsportsmanlike behaviour in the past, be it for throwing away her racquet or refusing to shake hands with opponents.
But she seems to have found inner peace this year.
"I need to be a little bit boring on court," Sabalenka told reporters.
"It's still about a lot of positive emotions for me, but I'm trying to stay away from negative (emotions) and just fight for every point."
Sabalenka said she wished she could have discovered the benefits of a less explosive approach earlier in her career.
"Finally I understand what everyone was looking for and asking for," she added.
"I think there were a few moments when I was about to throw my racquet or scream something. Because I hold myself really strong in those moments, after that I feel like it's a little bit more natural right now."
Bencic, of Switzerland, was just as assured in her 6-2, 7-5 victory over Italy's Camila Giorgi on Rod Laver Arena.
Sabalenka and Bencic are both on a roll this year in Australia.
They each won titles in Adelaide earlier this month, both are yet to drop a set in Melbourne and both are now on seven-match unbeaten runs.
Something will have to give when they clash on Monday for a place in the quarter-finals.
"Sabalenka is a very aggressive player, has a lot of power," said Bencic, who is aiming to become only the second Swiss woman to win the Australian Open after Martina Hingis, the 1997, 1998 and 1999 champion.
Bencic, who last week returned to the world's top 10 for the first time since 2021, has Sabalenka's former coach Dmitry Tursunov in her corner for the fourth-round encounter.
"Dmitry was her coach before, so he can help me a lot. I hope so," said Bencic.
