Daniil Medvedev has pulled off one of the great Australian Open comebacks, coming from two sets down to win a titanic struggle that finished after 3:30am.

Medvedev triumphed over Finland's Emil Ruusuvuori 3-6, 6-7(1/7), 6-4, 7-6(7/1), 6-0, in a match that lasted four hours and 23 minutes, and finished well after 3:30am local time.

The grand slam winner looked destined for an early exit at Melbourne Park has his Finnish opponent produced two immaculate sets of tennis to take the 2-0 lead.

But Medvedev, a former Australian Open finalist, used all of his experience to claw his way back, even when he looked at war with himself.

The match did not start until 11:15pm local time, due to a rain delay earlier on and the previous match — Anna Blinkova defeating Elena Rybakina — being decided by the longest tie breaker in women's grand slam history.

"This one if for sure going to stay in my memory, " Medvedev said in his post-match interview on court.

"Honestly guys, I would not be here — thanks for staying.

"If I would be a tennis fan and I would come [here], and 1[am] I would be 'ok, let's go home. We are going to catch the end of the match on the TV'.

"With tennis, you never know when you have to eat, when you have to warm up. So [tonight] it was too early, because I thought the [previous] match was going to be faster.

"I'm happy that I managed to stay tough, even if it was very tough."

Ruusuvuori made a breath-taking start against the former finalist at Melbourne Park, breaking his opponent's first service game on-route to taking the first set 6-3.

The pair traded breaks in the second set, leading to a tie breaker which the Finn was flawless.

Ruusuvuori won the first five points of the tie breaker, going on to wrap it up 7-1 and take a two set lead.

Medvedev, one of the finest hard court players in the world, was not going to throw in the towel and struck back in the third set.

The Russian broke serve early in the third set, then held the lead to get back into the match.