Australian Open title favorite Daniil Medvedev overcame a stubborn Maxime Cressy to reach the last eight, while French veteran Alize Cornet reached a Grand Slam quarterfinal for the first time in her career Monday.
It took the tetchy Russian world No. 2 around 3 hours 30 minutes to subdue the unseeded American serve-volley specialist Cressy 6-2, 7-6 (7/4), 6-7 (4/7), 7-5 to set up a quarter-final against Canada's Felix Auger-Aliassime.
"It was long and it was not easy, the scoreline apart from the first set were all tough sets," said Medvedev, who clashed with the umpire and complained of his bad luck during the most severe examination of his title credentials so far.
"If I didn't win the fourth set I would have been in a tough mental shape," he admitted.
Earlier, Cornet ended her last-16 hoodoo in her 63rd Slam and will now face Danielle Collins for a place in the women's singles semifinal.
The French veteran, who made her major debut in 2005 and turned 32 on Saturday, had reached the fourth round on five previous occasions, losing them all.
But she ended that run by upsetting former world No. 1 Simona Halep of Romania 6-4, 3-6, 6-4 in energy-sapping heat on Rod Laver Arena.
"It feels amazing. That battle I had with Simona today and the heat," said Cornet, who knocked out world No. 3 Garbine Muguruza in round two.
"After 30 minutes we were both dying and we kept going for two-and-a-half hours."
Collins had an even longer battle, the American outlasting Elise Mertens of Belgium 4-6, 6-4, 6-4 across 2 hours 51 minutes of bruising action.
"It was really tough for me," said Collins, who made the semifinals at Melbourne Park in 2019.
"I played a long match as well the other day so I had to make a lot of technical adjustments to be able to get myself moving around. That was a big challenge."
Aryna Sabalenka will round off the evening and stay on course for a first major if she can get past unseeded veteran Kaia Kanepi of Estonia.
The reward for the winner will be a quarterfinal against seventh seed Iga Swiatek of Poland who battled from a set down to beat Sorana Cirstea of Romania 5-7, 6-3, 6-3.
Unseeded Cirstea was on course for a big upset when she edged a tight first set.
But Swiatek, the 2020 French Open champion, gradually took control before winning in 2hours 27 minutes.
Men's ninth seed Auger-Aliassime overcame the 2018 Australian Open finalist Marin Cilic 2-6, 7-6 (9/7), 6-2, 7-6 (7/4) in 3hr 35min on John Cain Arena.
He joins Denis Shapovalov in the last eight to make it the first time two Canadian men have reached that stage at the Australian Open, and will now face Medvedev.
"It's amazing. It puts my belief even higher, I lost three times to Marin in the past, this is my first win against him and in an important moment like this," the Canadian said.
"I told him at the end of the match he's a champion, the way he handles himself and the way he plays and I knew he was going to come out with his best level and test me and make me earn my win.
"So I'm really relieved and happy to get through, especially the way I did it."
Later, world No. 4 Stefanos Tsitsipas beat Taylor Fritz 4-6, 6-4, 4-6, 6-3, 6-4 in an epic battle. The fourth seed had to fight back from two sets to one down to beat the American, who was playing in his first-ever last-16 match at a Grand Slam.
