Top seed Daniil Medvedev battled back from two sets down and saved a match point against Canada's Felix Auger-Aliassime to reach the Australian Open semi-finals with a 6-7(4) 3-6 7-6(2) 7-5 6-4 victory on Wednesday.

The 25-year-old Russian had his back firmly up against the wall for much of an absorbing contest as Auger-Aliassime produced some stunning tennis on Rod Laver Arena.

But he simply refused to lie down as he overturned a two-set deficit for only the second time in his career to set up a Friday semi-final against Greek Stefanos Tsitsipas who he beat at the same stage a year ago.

It was the kind of resilience absent nine-time champion Novak Djokovic has trademarked and Medvedev, the reigning U.S. Open champion, said he had taken inspiration from the Serbian to get out of trouble.

"At two sets down I was not playing my best and Felix was playing unbelievable, serving unbelievable, he was all over me to be honest. I didn't know what to do so I told myself 'what would Novak do?" Medvedev said on court, prompting some boos.

"What came to mind, was that I thought if Felix wants to win it he will have to fight for the last point.

"I managed to raise my level and when they closed the roof I felt the momentum and started serving better."

Ninth seed Auger-Aliassime, 21, was the dominant player in the first set and despite a wobble when serving at 6-5 he won a tiebreak courtesy of some Medvedev double-faults the Russian later blamed on the sweaty conditions.

Serving beautifully and playing with composure and precision from the back of the court, Auger-Aliassime cruised through the second set with a single break with Medvedev looking subdued.

Auger-Aliassime was one set away from a first career win against the Russian and a place in his second Grand Slam semi-final, but the night was still young.

Medvedev hung tough towards end of the third set as Auger-Aliassime sensed victory but he managed to force a tiebreakand closed it out after a shower caused the roof to be closed.

Serve dominated the fourth set but in the 10th game Medvedev coughed up a double-fault to hand his opponent a match point.

Medvedev barely blinked though and escaped with some powerful serving. He then pounced in the next game to break serve as Auger-Aliassime sent a forehand wide, before holding his own to extend the match into a decider.

With the match moving into its fifth hour, Medvedev finally seized control with an early break of serve but Auger-Aliassime did not crumble.

The Canadian earned a break back point trailing 4-3 but Medvedev snatched away the opportunity with a timely ace and then had Medvedev down 15-40 as the Russian served at 5-4.

Medvedev dialled up his inner Novak once again, however, reeling off the next four points to claim an epic victory after four hours and 42 minutes.