Italian fourth seed Jannik Sinner began his Australian Open campaign with a straight-set win, while Andrey Rublev won a five-set thriller to reach the second round.

Sinner, 22, beat Dutchman Botic van de Zandschulp 6-4 7-5 6-3.

Fifth seed Rublev survived a comeback from world number 78 Thiago Seyboth Wild to win 7-5 6-4 3-6 4-6 7-6 (10-6).

Djokovic, chasing a record-extending 11th men's title, plays teenager Dino Prizmic in Sunday's night session.

Former semi-finalist Matteo Berrettini withdrew before his first-round match against Stefanos Tsitsipas because of a right foot injury, meaning the Greek seventh seed will instead play Belgian Zizou Bergs.

Russian Rublev missed four match points in the final set but took the fifth during the deciding tie-break over Brazilian Seyboth Wild, dropping backwards to lie on the court in celebration.

"For sure, I will not forget this match," Rublev said in his on-court interview.

"Thiago is a super dangerous player, super talented. He hits so hard and so clean, it is so hard to beat him. He was serving so hard, not many double-faults, he could hit a winner from any position."

Elsewhere in the men's draw, Croatia's 2018 runner-up Marin Cilic lost 6-1 2-6 6-2 7-5 to Hungarian Fabian Marozsan.

He will play Francisco Cerundolo next after the Argentine 22nd seed came out on top in five sets against Australian Dane Sweeny, winning 3-6 6-3 6-4 2-6 6-2.

The Australian Open has been extended to 15 days this year in an attempt by organisers to avoid late finishes - with this its first Sunday start.

Sinner inspired by Carota Boys' support

Sinner would become the first Italian player to reach an Australian Open singles' final if he can achieve his best ever Grand Slam result at Melbourne Park this fortnight.

Italy's rising star Sinner, who led his nation to the Davis Cup title in November, made a solid start to his campaign and took the first two sets with a single break of serve.

He found himself behind in the third as world number 59 Van de Zandschulp survived four break points before taking his first for a 2-0 lead.

But Sinner responded emphatically, winning six of the following seven games to close out a comfortable victory on the opening day and set up a second-round meeting with Argentine Pedro Cachin or Dutch qualifier Jesper de Jong.

"My first match of the season and it means a lot to start off with a win," said Sinner, who was cheered on by the 'Carota Boys' - his fans who attend his matches dressed as carrots after seeing him eat one during a match in Vienna in 2019.

"Physically, I feel good in good shape, the first round is never easy so I can be happy with today."

On the backing he receives from his loyal supporters, he added: "It feels good. I was not expecting them to come here, but it's nice to see them in the stands.

"Obviously, we have made some great memories together, with all the support they give me. They are getting more famous than I am slowly.

"Maybe this support gives me in the key moments this extra belief maybe. Who knows? Let's see how it goes here. But I'm happy that they are here."