Britain's Andy Murray produced a stunning comeback to claim victory over Australian Thanasi Kokkinakis in a five-set thriller that ended at 4:05 a.m. local time in Melbourne.
The 35-year-old Scot looked down and out against an inspired Kokkinakis as he trailed by two sets and 2-5 but displayed his trademark warrior spirit to somehow claw out a 4-6 6-7(4) 7-6(5) 6-3 7-5 victory after five hours and 45 minutes.
Murray will face Spain's Roberto Bautista Agut in the third round -- the man who beat him at the 2019 Australian Open, after which Murray's career appeared to be over because of the hip condition.
It was another stupendous effort from three-time Grand Slam champion Murray whose career has been littered by such battles.
Kokkinakis, 26, whose own career has been too often blighted by injuries, dominated the opening two sets with the kind of aggressive tennis and ball-striking that made a mockery of his No. 159 ranking.
Murray's resistance looked over when Kokkinakis led 5-2 in the third set with the Australian on the verge of his biggest career win. but the Brit would not go away.
Kokkinakis got tight with the finishing line in sight and the venom gradually went out of his shots as Murray threw caution to the wind and locked on to his target.
Relentlessly, Murray ground his way back into the contest to set up a deciding fifth set, sealing the fourth set with a second-serve ace.
A weary-looking Kokkinakis did not capitulate and the raucous atmosphere inside the stadium revived him early in set five as he kept his nose in front on serve.
There was pandemonium when he saved four break points at 3-3, and Kokkinakis was within two points of victory when Murray served at 4-5 in the decider.
But Murray's greater experience of such duels enabled him to get the crucial break of serve in the following game with a stunning forehand winner before sealing victory in the next game on his first match point with a backhand winner.
Earlier on Thursday, Britain's Daniel Evans beat France's Jeremy Chardy 6-4, 6-4, 6-1 to progress to the third round of the Australian Open.
Evans, 32, rallied to defeat Chardy in under two hours to set up a tie with World No. 6 Andrey Rublev.
But it was Chardy who won the attention of many with an outburst at the chair umpire in the first set. Facing a break point, a ball dropped out of the Frenchman's pocket midway through a rally and he put a forehand into the net with his next shot to lose the point.
Chardy immediately appealed to the chair umpire but Miriam Bley ruled that the point would not be replayed, with Evans pointing out that he neither saw the ball drop out of the pocket nor did he complain about it.
"We play with someone who cannot umpire," Chardy said. "In my life, 20 years I've never had one umpire bad like you. Where are you looking? You looking at the birds? The clouds?
"It's the biggest mistake of the Australian Open. There's not one umpire on tour that does this mistake, not one."
He then called for a supervisor and said: "If you don't confirm that I called let, I lose all respect for you. She's lying. Can she have a fine? When we do something bad we are fined, can she have a fine?"
Evans did not agree with Chardy's suggestions that the point should be replayed.
"I think the rule should be if a ball comes out of your pocket, you lose the point," he said. "He missed the ball.
"If a ball comes out your pocket, it's your own fault."