The Nick Kyrgios rehabilitation regime will undergo its first big test of the summer as the mercurial star gets his Melbourne Park campaign underway with a dozen other Australians on Tuesday.

Getting warm support following his fundraising efforts for the Australian bushfires, Kyrgios nonetheless finds himself walking a tightrope with a 16-week suspended ban hanging over his head.

While he acquitted himself well at the ATP Cup, he admitted being far more relaxed in the team environment with the season-opening grand slam and best of five set matches expected to be much more of a physical and mental challenge for him.

He says Italian opponent Lorenzo Sonego will also present his share of problems.

“Sonego is a tough competitor,” Kyrgios said.

“I played him in Cincinnati last year. It was a tough match. Very capable player. Big serve. Loves to hit his forehand.”

On Monday rain restricted all but the earliest of matches to the three covered courts but after some morning showers things are expected to clear on Tuesday where a jam-packed schedule awaits.

Alexei Popyrin has an intriguing match against 2008 finalist, Jo-Wilfried Tsonga.

The world No.96 will be looking to continue on from last year’s admirable grand slam efforts, where he won through every first round match.

At the Australian Open he took out two-time French Open finalist Dominic Thiem.

John Millman faces a tough clash with Ugo Humbert, the 21 year-old Frenchman in excellent touch after taking out last week’s Auckland International.

Jordan Thompson and Ajla Tomljanovic head the rest of the local hopes.

Of the internationals a slew of tournament fancies are scheduled to get their campaigns underway.

World No.1 Rafael Nadal looks to have the most straightforward of matches, the Spaniard up against 73rd-ranked Bolivian Hugo Dellien.

Elsewhere things get a little more interesting.

Daniil Medvedev is expected to encounter some opposition from 2019 quarter-finalist Frances Tiafoe while Simona Halep will have to counter the heavy hitting of Jennifer Brady.

And Alexander Zverev has tought first-up clash with Marco Cecchinato.

Despite him being lauded as one of the ‘next-gen’ talents likely to breakthrough for a grand slam, Zverev hasn’t always lived up to expectations, particularly at major level.

The German has yet to progress past the last eight at a slam while his much more unheralded opponent made the semi-finals of the French Open in 2018.