Melbourne: Novak Djokovic and Coco Gauff were both made to toil for semifinal places on a blazing Tuesday at the Australian Open.
Two epic battles in the afternoon meant defending women's champion Aryna Sabalenka did not walk onto Rod Laver Arena until well after 9 pm local time but the Belarusian made short work of Barbora Krejcikova to ease some of the pressure on the schedule.
Holder Djokovic was expected to breeze past Taylor Fritz having come into the contest with an 8-0 win-loss record over the 12th seed but he endured a stern test that lasted nearly four hours to prevail 7-6(3), 4-6, 6-2, 6-3.
"This match was not an enjoyable match for me at all," Djokovic told reporters.
"Of course, I'm proud to overcome the kind of challenge and obstacles and I'm pleased to win but it wasn't enjoyable at all. It was really ... a lot of suffering in every aspect.
"You have days like that where you just have to accept it, face the circumstances and try to make the most out of it."
Fritz, who at 26 is a decade younger than his opponent, made the Serb sweat in a tight first set that the American dropped in a tiebreak before drawing level in the contest on a steamy day where both players looked physically drained at times.
"I played a really high level for the first two sets and they were physically tough. It was like two-and-a-half-hours hours by the time we finished the two sets," said Fritz.
"I need to get to the point where I can do that for five hours."
Djokovic might have had starting troubles in his bid to win an 11th Melbourne Park title and 25th Grand Slam to eclipse the record of Margaret Court but he is an expert problem solver and took advantage of a tiring Fritz to prevail.
Gauff was happy to win "ugly" as she quelled the challenge of Ukrainian Marta Kostyuk 7-6(6), 6-7(3), 6-2 in a little over three hours and the US Open champion will need to raise her level if she hopes to win a second Grand Slam title.
"Yeah, it was a fight," said Gauff, who had to battle back from 5-1 down in the opening set. "I think today was definitely a 'C' game, so didn't play my best tennis but really proud that I was able to get through today's match.
"Hopefully I got the bad match out of the way and I can play even better."
Kostyuk said she felt like a winner despite the loss having helped give fresh attention to the war raging in her country nearly two years after Russia's invasion.
Her compatriot Dayana Yastremska also made it to the last eight at the year's first major, while Elina Svitolina had to retire in the fourth round.
"I think the girls did really well," Kostyuk said. "I hope we'll be able to succeed in most of the tournaments, especially the big ones where there's a lot of media."
Sabalenka continued her merciless progress with a 6-2, 6-3 victory over 2021 French Open champion in 71 minutes to book a meeting with Gauff - a rematch of their Flushing Meadows title clash where the American prevailed to win her first major.
"I think it was a really great match today. I played really great tennis and I really hope I can just keep playing that way or even better," Sabalenka said.
"Thank you so much for the atmosphere. I know you're waiting for the next match but I enjoyed it.
"It reminded me of the (Australian Open) final last year."