Third seed Alexander Zverev will face John Millman and a parochial home crowd after an unconvincing Australian Open first-round win over fellow German Daniel Altmaier.

The 24-year-old gun was tested by unfancied Altmaier on Monday night but did enough to prevail in straight sets, 7-6 (7-3) 6-1 7-6 (7-1).

Zverev sent down 14 aces and clubbed 53 winners against an opponent ranked 87 in the world, who had only competed at one previous grand slam tournament.

But the performance was far from Zverev's best - not that it bothered him too much.

"Not much went to plan today, to be honest, except that I won," Zverev said.

"That's how it is sometimes.

"It's the first round of a hopefully very long tournament and you're not always going to play your best tennis - unless you're Roger (Federer) or Rafa (Nadal) and you're always perfection.

"But I'm not like them.

"It was a good match for me to get into the tournament and hopefully the next one will be better."

Zverev, who won Olympic gold in Tokyo last year, is looking to cash in on the absence of nine-times Open champion Novak Djokovic and injured Swiss master Federer to claim his first grand slam title.

He has reached the final four of a slam three times in the last two years, including a semi-final defeat to Dominic Thiem at Melbourne Park in 2020.

But Millman, who overcame Spain's Feliciano Lopez 6-1 6-3 4-6 7-5 on Monday, presents as a potential banana-skin for Zverev.

The 32-year-old Australian pushed Zverev to five sets in their previous meeting at a grand slam tournament - in the first round of the 2019 French Open.

"He's a very difficult player to beat, especially in here Australia," Zverev said.

Millman urged local fans to get behind him in his bid to cause what would be a huge upset.

"You have to be playing amazing tennis to match it against the top players," Millman said.

"Alexander Zverev, especially after the year he had last year and Olympic gold, so consistent week-to-week.

"He's a great player, he's got a great first serve, probably one of the best two-handed backhands on the tour.

"I played him a few times, I played him in a major before ... so hopefully we can get on a big court, the crowd can really get behind me and I'll give it my all."