Brisbane, QLD, 3 January 2020 | Laine Clark (AAP)

Two years after he first faced an unheralded Alex de Minaur, German tennis superstar Alexander Zverev has rated the Australian as the ultimate test ahead of their opening ATP Cup clash on Friday.

World No.7 Zverev said Germany were full of confidence before facing Australia in their ATP Cup opener at Brisbane’s Pat Rafter Arena – the same venue where they downed the hosts 3-1 in a 2018 Davis Cup clash.

But Zverev was wary of De Minaur after the Australian’s remarkable rise since their memorable first meeting in their Davis Cup tie two years ago.

A fresh-faced De Minaur was the lowest ranked Australian in the team at No.139 when he was a shock singles pick for the Davis Cup clash. However, he still gave Zverev a scare before losing their opening singles rubber in an epic five setter.

Fast forward two years and the 20-year-old de Minaur is now Australia’s undisputed No.1 player at the ATP Cup, spearheading the team as the world No.18.

Not that Zverev had to be reminded.

The German has clearly been monitoring the Australian’s dramatic progress, admitting De Minaur would provide a timely 2020 yardstick.

Zverev has been heralded as a potential Grand Slam champion since becoming the youngest winner of the ATP Finals in a decade when he emerged triumphant in 2018 but has never been able to advance beyond the quarterfinals at a major tournament.

Now 22, Zverev hinted that his ATP Cup clash with De Minaur would indicate whether he was on track to make a Grand Slam breakthrough this year.

“I will know exactly where I stand after that match,” Zverev said of his ATP Cup clash with the Australian.

“Of course he’s improved (since 2018). Back then he was an up and coming young guy and now he’s top 20 in the world.

“At that Davis Cup match here he was the best one that we played.

“It’s not easy against him because he’s not somebody that will give you a lot – it’s going to be a very difficult match.”

De Minaur typically played the modest card before their clash but hinted that he was ready for whatever Zverev could throw at him after taking less than two weeks off in the off-season.

“I think I’ve put in a lot of hard work through the pre-season and I feel ready for a new year,” he said.

Germany’s clash with Australia looms as Friday’s highlight of the 10-day, 24-team ATP Cup which will hold round robins clashes in Brisbane, Perth and Sydney before finals are staged in Sydney.