Top seed Daniil Medvedev snatched victory from the jaws of defeat on Wednesday to reach the Australian Open semi-finals.
World No2 Medvedev looked down and out as he lost the opening two sets against Canada's Felix Auger-Aliassime before staging a comeback.
The Russian saved a match point at 4-5, 30-40 in the fourth set before completing the turnaround to beat the ninth seed 6-7 (4/7), 3-6, 7-6 (7/2), 7-5, 6-4 in a marathon quarter-final that lasted four hours and 42 minutes and finished well after midnight on Rod Laver Arena.
Asked how he managed to win, Medvedev admitted: "I have no idea. I just fought to the last point and manage to raise my level.
“I was not playing my best, and Felix was playing unbelievable, serving unbelievable - he was all over me,” Medvedev added. “I didn’t know what to do so I [asked] myself, ‘What would Novak do?’
“And I just thought, OK, I’m going to make him work. If he wants to win it, he has to … fight to the last point.”
It sets up a repeat of last year's semi-final against Stefanos Tsitsipas, which Medvedev won in straight sets before going on to lose to Novak Djokovic in the championship match.
Tsitsipas, meanwhile, extended his perfect record in Grand Slam quarter-finals after delivering a masterclass to thrash Jannick Sinner and book his place in the Australian Open last-four.
The Greek fourth seed was at his scintillating best inside Rod Laver Arena, where he raced to a 6-3, 6-4, 6-2 win over the 10th-seeded Italian in just over two hours.
With Melbourne's big Greek population, Tsitsipas has always drawn strong support at the Australian Open and it was the same again in the clash against Sinner.
"I think my humility helped a lot today. I knew I was going on the court facing a very good player. I tried to focus on my best shots and it paid off more than I thought," he said in his on-court interview.
"Once again, stepping on to that court, having the crowd support, it is truly unbelievable."
Tsitsipas had been troubled by an elbow injury ahead of the Australian Open, and following the gruelling five-set win over Taylor Fritz in the fourth round on Monday, the in-form Sinner was expected to test the Greek's fitness and energy levels.
Instead, Tsitsipas stamped his authority from the get-go, breaking at the first opportunity and keeping Sinner at arms-length to cruise to the first set. Another break early in the second - shortly before a rain interruption which forced the stadium roof to be closed - again proved enough of an advantage as Tsitsipas dominated his own service games.
With the fight knocked out of Sinner, Tsitsipas broke twice in the third set to wrap up an emphatic victory to send out an ominous warning to his remaining rivals and dismiss any doubts about his fitness.
Meanwhile, Iga Swiatek said she was proud of how she battled from a set down to make her maiden Australian Open semi-final. The Polish seventh seed proved too resilient for gutsy veteran Kaia Kanepi, ending the unseeded Estonian's surprise Melbourne Park run 4-6, 7-6 (7/2), 6-3.
It set up a clash with American Danielle Collins - who earlier defeated Frenchwoman Alize Cornet 7-5, 6-1 - for a place in the final.
