Novak Djokovic was given a brief scare by Croatian teenager Dino Prizmic in the longest first-round match of his grand slam career.
The world number one is a hot favourite to win an 11th title at Melbourne Park, where he has not lost since 2018, but he dropped the second set as 18-year-old Prizmic showed what makes him a major talent for the future.
The qualifier was briefly a break up in the third set and kept battling after Djokovic stepped things up before the defending champion finally clinched a 6-2 6-7 (5-7) 6-3 6-4 victory on his seventh match point after four hours and one minute.
This is Djokovic's 73rd grand slam tournament and he was full of praise for debutant Prizmic, saying: "He deserved every applause, every credit that he got tonight.
"He’s an amazing player I must say, so mature for his age. This is his moment and it could easily have been his match as well. He made me really run for my money for sure tonight. Amazing performance for someone that is 18 years old that has never had experience of playing on this stage.
"I certainly want to be in his corner, so hopefully he will invite me because we’re going to be seeing a lot of him in the future."
The signs did not look good for Prizmic when he dropped his opening service game and then took a medical timeout at 2-3 for treatment to his left groin.
He already had tape on his right arm and could find nothing to hurt Djokovic in the first set, but things began to change early in the second.
Djokovic won a staggering 17 of his 19 tiebreaks at grand slams in 2023, including 15 in a row from the second round in Melbourne to the Wimbledon final, but here he played a very poor one and suddenly what had seemed a straightforward occasion became anything but.
Djokovic, who was dabbing his brow and puffing his cheeks, was making a lot of uncharacteristic errors and Prizmic fought back from 2-0 down in the third set to lead by a break at 3-2.
There was concern on the face of Djokovic’s coach Goran Ivanisevic, who was among the spectators watching his countryman Prizmic’s run to the French Open junior title last year.
Djokovic ultimately found a way through, but the 36-year-old’s rivals will have been watching closely.
"I’m double his age," said the 10-time champion with a rueful smile. "Reality hits hard tonight. I struggled in many different moments, but he had an answer for everything. Now I have a couple of days, so hopefully I’ll be able to be at my best for the next match."
Jannik Sinner picked up where he left off in 2023 by easing past Botic van de Zandschulp into the second round.
Italian fourth seed Sinner, the hottest player on the men's tour at the back end of last season with victories over Novak Djokovic, Carlos Alcaraz and Daniil Medvedev, was quickly back in his groove on Rod Laver Arena.
Although far from perfect, he broke his Dutch opponent to open the contest and grabbed another break to serve for the second set before securing his place in the second round 6-4 7-5 6-3.
"It's my first match of the season and it means a lot to get a win," said Sinner, who was cheered on by the "Carota Boys", a band of fans dressed as carrots.
"It's a tournament where I would like to play as good as possible ... hopefully I can show more as I go along. The first match is never easy, I think I can be happy."
At 26, Andrey Rublev is probably a bit old to be considered a young gun and the redheaded Russian had a much tougher time getting into round two, pushed all the way by debutant Thiago Seyboth Wild in his 7-5 6-4 3-6 4-6 7-6 (8-6) win.
The often emotional Rublev was clearly furious at his inability to see off the Brazilian world number 78, who produced some sensational shots to frustrate the fifth seed and earn the support of the Margaret Court Arena crowd.
Seyboth Wild, who stunned Medvedev in the first round of last year's French Open, saved three match points at 6-5 down in the decider and raced to a 3-0 lead in the tiebreak before Rublev rallied for the victory.
"I'm not going to forget this match," said the relieved Russian.
"I was thinking about Daniil's match at Roland Garros when I had my chances and couldn't take them.
Thiago is a super dangerous player, he was serving really hard, first and second serves, and hitting the ball really clean."
Marin Cilic reached the final in 2018 but he had little to celebrate after his 50th match at Melbourne Park, a 6-1 2-6 6-2 7-5 loss to Hungarian Fabian Marozsan.
As usual, big crowds flocked to the Melbourne Park precinct for the year's first grand slam even if there was no Nick Kyrgios to cheer on this year.
Local qualifier Dane Sweeny gave fans on Kyrgios's favourite court plenty to shout about in his gutsy 3-6 6-3 6-4 2-6 6-2 loss to Argentine Francisco Cerundolo on John Cain Arena.
"The crowd was unreal," said Sweeny. "I was really happy to take it to a fifth and push him to the very end."
Former Wimbledon finalist Matteo Berrettini was a casualty without taking to the court, the Italian pulling out as his injury woes continued.
Berrettini had been due to face Stefanos Tsitsipas on Rod Laver Arena on Monday in one of the plum ties of the first round.
But on Sunday afternoon tournament organisers announced he had withdrawn with a right foot injury, making it the fourth time in the last eight grand slam tournaments where he has not been able to play a match.
