Djokovic and Gauff labour into Australian Open semis, Sinner and Sabalenka sprint

MELBOURNE, (Reuters) - Novak Djokovic and Coco Gauff were both made to toil for semi-final places on a blazing Tuesday at the Australian Open but organisers were spared a ridiculously late finish as Aryna Sabalenka and Jannik Sinner roared through the night session.

Two epic battles in the afternoon meant defending women's champion Sabalenka did not walk onto Rod Laver Arena until well after 9 p.m. but the Belarusian made light of Czech Barbora Krejcikova, winning 6-2 6-3 to ease pressure on the schedule.

Fourth seed Sinner then beat fifth seed Andrey Rublev 6-4 7-6(5) 6-3 just before 1.30am to set up a mouth-watering clash with Djokovic and leave a shattered Rublev picking over a 10th defeat in 10 Grand Slam quarter-finals.

Holder Djokovic was expected to breeze past Taylor Fritz having come into the contest with an 8-0 win-loss record over the 12th seeded American but he endured a stern test that lasted 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 2-1/2 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 has had some tough moments on his way to reaching his 48th Grand Slam but is now two wins away from a record-extending 11th Melbourne Park title and 25th Grand Slam to eclipse the record he shares with Margaret Court.

Invariably he finds a solution and Gauff was forced to do the same against Ukraine's Marta Kostyuk, admitting she had to win "ugly" as she triumphed 7-6(6) 6-7(3) 6-2 in a scrappy match lasting a little over three hours.

"Yeah, it was a fight," the U.S. Open champion Gauff, who had to battle back from 5-1 down in the opening set, said.

"I think today was definitely a 'C' game. Hopefully I got the bad match out of the way."