Bidding to be the first woman since Victoria Azarenka in 2013 to claim back-to-back Australian Open crowns, Sabalenka beat American Amanda Anisimova 6-3 6-2 in an hour and 10 minutes on Sunday.
"I'm super happy with (my) level, happy to get this win," the 25-year-old said after Sunday's fourth-round encounter.
"She's a tough opponent and I'm super happy to see her back on tour and I'm pretty sure she'll be back in the top players very soon.
"I really want to stay here as long as I can, until the very last day."
The world No.2 time had dropped six games on her way to the fourth round at Melbourne Park but appeared poised to be tested by Anisimova, based on the pair's head-to-head record.
Anisimova had beaten the powerhouse Belarusian in four of their past five meetings.
In fact, the world No.442 - who entered the tournament through a protected ranking - trounced Sabalenka twice in straight sets, at Melbourne Park and Roland Garros in 2019.
But Sabalenka has since vaulted to another stratosphere and showed no lingering trauma from that poor record, taking just 36 minutes to wrap up the first set.
Anisimova's frustrations boiled over moments after the straight-sets loss was sealed as she sent her racquet flying.
Sabalenka will meet 2021 French Open winner Barbora Krejcikova after the Czech defeated 16-year-old Russian sensation Mirra Andreeva 4-6 6-3 6-2.
Andreeva won the first set as she aimed to be the youngest player since Martinia Hingis 27 years ago to make the quarter finals of the Australian Open.
But as she did in her third-round win against Australian Storm Hunter, Krejcikova grew better as the match went on to end Andreeva's brilliant run at Melbourne Park.
Sabalenka is the highest seed left in the women's draw after world No.1 Iga Swiatek followed last year's Open runner-up Elena Rybakina out the door on Saturday night.
Gauff shapes as Sabalenka's likely semi-final opponent after the 19-year-old American gave short shift to Magdalena Frech earlier on Sunday.
Watched by Australian tennis legend Rod Laver on the court named in his honour, Gauff dismantled the Polish world No.69 6-1 6-2 in little more than an hour.
It's the first time Gauff, the fourth seed, has made it past the fourth round of the Australian Open.
Playing in her last major as a teen, the Atlanta native has spent just four hours and 48 minutes on court through the first four rounds but insisted she wasn't in a hurry on Sunday.
"I want to see The Iron Claw tonight. I want to go to the movies," Gauff joked in her on-court interview, after extending her winning streak to nine matches following her title run in Auckland.
"No, I'm not in a rush to go anywhere. There's no better court in Australia than Rod Laver (Arena), and it was an honour to play in front of you."
Gauff never faced a break point and smashed 21 winners to lock in a quarter-final encounter with Ukraine's Marta Kostyuk, a 6-2 6-1 winner over Russian qualifier Maria Timofeeva.
7°C