Rafael Nadal sailed into the second round of the Australian Open on day two before backing "humble" fellow Spaniard Carlos Alcaraz to have a "great career" following his maiden grand slam win.

Nadal cruised to a 6-3 6-4 6-1 victory over Laslo Djere on Rod Laver Arena on Tuesday and will face Michael Mmoh in round two.

The Spanish great's compatriot Alcaraz won his first major match at Melbourne Park, seeing off fellow qualifier Botic Van de Zandschulp 6-1 6-4 6-4.

Murcia native Alcaraz has been billed by Nadal's uncle and former coach, Toni Nadal, as his nephew's "natural replacement" and the 20-time grand slam champion says the 17-year-old has all the ingredients to have a great career.

The second seed said: "He's very good. He's very young. He has everything to improve in the future with his age.

"He already is where he is, and he has a lot of great things on his game. I really believe that he will have a great future because he's a good guy, humble, hard worker. He has a lot of positive things."

Daniil Medvedev outclassed Vasek Pospisil 6-2 6-2 6-4, while Stefanos Tsitsipas eased past Gilles Simon 6-1 6-2 6-1, but fellow seed David Goffin lost a five-set marathon with Alexei Popyrin.

Nadal happy to 'survive' 

Nadal missed the ATP Cup before starting his quest for a record 21st grand slam title at Melbourne Park due to muscle tightness in his back.

He was simply happy to clear the first hurdle on the second day of the tournament.

"I needed to survive today and that's what I did. I just tried to be focused all the time, tried to get through," he said.

"For me personally, [I'm] happy to be through to the second round. I did I think a good job today. Straight sets, that's what I did."

Tennys disgruntled over 'joke' of preparation

American Tennys Sandgren was among over 70 players who were locked down in a hotel for a fortnight before the tournament due to positive COVID-19 test on their flight to Australia.

Sandgren made no secret of his displeasure over the restrictions he was forced to adhere to and let his feelings be known again after the two-time quarter-finalist lost 7-5 6-1 6-1 to Alex de Minaur on John Cain Arena.

He said: "How would you imagine prepping for a hot kind of muggy day, three-out-of-five sets against a player like that, that calibre, when you can't play tennis? You can't go outside? You can't. It's impossible. It's impossible.

"So I played last week's event [the Great Ocean Road Open], which probably wasn't a good idea. It wasn't hot, it was very mild conditions, and I played two hard three-set matches and I've never been more sore in my life after the second round, and I took two days off because I couldn't walk, and then I hit a couple times before today. I mean, it's just kind of a joke of preparation. But yeah. What are you going to do?"

Alcaraz escaping social media hype

Big things are expected of teenager Alcaraz and there was more hype over his potential after an impressive first-round win.

Alcaraz just wants to do his own thing and show why the likes of Rafael and Toni Nadal speak so highly of him.

"So I try to be focus on me, not on the social media, to play my game, play in front of my team, to my team, to me, my family," he said.

"I try to, yeah, to be a part of the social media and don't hear the comparison with Rafa. Yeah, I try to do this."