But home favourite Nick Kyrgios will not join them as the combustible Australian failed to clear the first hurdle, swearing and in pain.

In the women's draw, Iga Swiatek and Coco Gauff powered through with minimum fuss as they seek to dethrone two-time defending champion Aryna Sabalenka.

On a blockbuster second day in Melbourne, Djokovic lost the first set to 107th-ranked American Nishesh Basavareddy in the prime-time evening match on Rod Laver Arena.

But the Serbian great, hoping to roll back the years and win an 11th Australian Open and record 25th Grand Slam singles title, recovered to pull through 4-6, 6-3, 6-4, 6-2.

Djokovic was animated at the end and struggled to raise a smile.

Italian world number one Sinner was playing under a cloud after twice testing positive for traces of a steroid in March.

He denies wrongdoing and was cleared by tennis authorities, but the World Anti-Doping Agency (WADA) appealed and is seeking to ban him for up to two years.

Sinner was warmly welcomed on Rod Laver Arena before defeating Chile's Nicolas Jarry 7-6 (7/2), 7-6 (7/5), 6-1.

"I was curious to see how it was. You never know what's happening," he said about the reception.

"I was happy about the crowd," said Sinner, who has not tasted defeat since losing to Alcaraz in the Beijing final in October.

Alcaraz, a four-time Grand Slam champion but never a winner in Melbourne, had a couple of hairy moments before seeing off the challenge of Kazakhstan's Alexander Shevchenko, 6-1, 7-5, 6-1.

"This is a tournament I really want to win one day, hopefully this year," said the 21-year-old Spaniard.

There was disappointment however for home fans as the colourful but temperamental Kyrgios, only recently back from 18 months out with injury, lost 7-6 (7/3), 6-3, 7-6 (7/2) to Britain's Jacob Fearnley.

Kyrgios spoke to physios multiple times in the second set after wincing in pain while serving and fired expletives at his coaching box.

Earlier, the 11th-seeded Stefanos Tsitsipas became the first major casualty when Alex Michelsen blasted past him 7-5, 6-3, 2-6, 6-4.

The 26-year-old Greek, who played Djokovic in the 2023 final at Melbourne Park, never looked comfortable against the 42nd-ranked American.

"It just sucks in a way that I'll be hanging around for quite a while now before my next tournament comes in," said Tsitsipas.

Two-time US Open semi-finalist Frances Tiafoe vomited twice on court before pulling through in five sets against Frenchman Arthur Rinderknech.

- Gauff sends warning -

The women's draw provided few upsets on day two.

Red-hot world number three Gauff laid down a marker as she swept aside former Melbourne champion and fellow American Sofia Kenin.

Gauff is unbeaten this year after leading the US to United Cup glory and eased past the 2020 Australian Open winner 6-3, 6-3 in 80 minutes.

"I knew it was going to be difficult, but you know, I'm happy with how I played," said Gauff, the 2023 US Open champion.

Women's world number two Swiatek defeated Czech doubles specialist Katerina Siniakova 6-3, 6-4 to get her tournament up and running.

The Pole has won five Grand Slams but her best performance at Melbourne Park is the semi-finals in 2022.

"For sure it wasn't an easy first round, so I'm happy that I'm through," said Swiatek.

Victoria Azarenka, the 2012 and 2013 champion, was a notable early loser as the Belarusian went down 6-2, 7-6 (7/2) to Italy's Lucia Bronzetti.

US Open finalist Jessica Pegula, the seventh-seeded American, blew away home player Maya Joint 6-3, 6-0.

Japan's Naomi Osaka, a two-time Australian Open champion, later faces 67th-ranked Caroline Garcia in a repeat of last year's first-round clash that the French player won.