The world number one had to battle hard to beat Denmark's Clara Tauson 7-6 (7/5), 6-4 in the third round and reach the second week in Melbourne.

But her serving woes, which plagued her in the previous round, dogged her again in a roller coaster scrap that lasted more than two hours on Rod Laver Arena.

"Conditions are pretty heavy for servers," Sabalenka told reporters.

"It's not giving you that much advantage as usual. Balls are heavy. Courts are a little bit slower. You have to sometimes just put that serve in and play the rally."

Sabalenka had wobbled badly in her second-round win against Jessica Bouzas Maneiro, dropping her serve three times.

On Friday it was even worse and Sabalenka was broken in the opening game by world number 42 Tauson.

It was the first of seven consecutive breaks between the pair -- four by the top-ranked Belarusian -- before Tauson belatedly held for a 5-3 lead.

That sparked Sabalenka into life as she finally held her own delivery to love then broke back again.

Sabalenka squandered four set points on the Tauson serve at 6-5.

On Sabalenka's fifth set point in the tiebreak she made no mistake, a rasping forehand winner putting her ahead.

"I think winning the first set -- it was a very difficult set -- gave me a little bit more mental strength that I can win this match even without serving my best," said Sabalenka.

She dropped her serve once more in the second set but fought back again until, at 4-4, the pair exchanged a succession of sizzling winners.

'Great battle' 

It resulted in the longest, most intense game of the match featuring seven deuces until Sabalenka secured the crucial break.

Sabalenka still had to save two more break points from the plucky Tauson, before clinching the match in 2hr 6min.

"That was a great battle," said Sabalenka.

"She played unbelievable tennis. It was really tough to play against her today. I'm just super happy that I was able to just stay in the game and I was able to push myself, honestly, to the limit.

"It was really important to get all of those breaks back. It could have gone either way."

Both players were seeking to extend their 2025 unbeaten streaks to eight matches after Sabalenka won the Brisbane International warm-up and Tauson clinched the title in Auckland.

In the end it was a 17th consecutive victory on Rod Laver Arena for Sabalenka.

Next up is either rising Russian teenage star Mirra Andreeva or Poland's Magdalena Frech.

Sabalenka is hunting down a rare hat-trick of consecutive Australian Open titles, a feat last achieved 26 years ago by Martina Hingis and only matched by four other women in history.

Two-time Melbourne champion Naomi Osaka was on a collision course with American third seed Coco Gauff in the next round.

But the former world number one needed treatment on her stomach from the trainer during the first set against Belinda Bencic and called it quits after losing the opener on a tiebreak.

Osaka, who was struggling with an abdominal injury in the build-up to the tournament and retired from the final in Auckland, was in the third round of a Slam for the first time since the birth of her daughter in 2023.