Eight-time Grand Slam champion Andre Agassi has anointed Novak Djokovic as the greatest men's player of all time, saying you cannot argue with the weight of his achievements.

The popular American former world number one, himself widely considered among the best the sport has seen, also had lavish praise for Roger Federer and Rafael Nadal.

But he said numbers do not lie.

"There's so many ways to look at it, but when you look at it on paper you just can't argue with what he's accomplished," Agassi told The Australian newspaper in Melbourne, where he is attending the opening Grand Slam of the year.

"The amount that he's won, the head-to-heads, the Masters (titles), the year-end number ones, the weeks at number... all those stats."

Like Djokovic, Agassi played some of his best tennis at Melbourne Park, with four of his major titles coming at the Australian Open -- in 1995, 2000, 2001 and 2003.

But they pale against the Serb's 10, with the 36-year-old favourite to add an 11th this year, which would take his Slam total to an all-time record 25, surpassing Margaret Court's 24.

Nadal, who pulled out of this year's Australian Open with a muscle tear, has won 22 Grand Slams and the retired Federer, 20.

"Novak has won more Australian Opens than I've won Slams for crying out loud... what do you do but laugh? I don't know what to say to that," said Agassi.

The 53-year-old, who bagged 60 career titles, including an Olympic gold, said Djokovic, Federer and Nadal had all brought so much to the game.

"I'm such a traditionalist for the game itself... when I look at what people bring to the sport, he (Djokovic) has brought so much, unquestionably," he said.

"But then you look at what Roger has brought to the sport -- the elegance and the class and the way that he did it.

"And then Nadal, the intensity or the ballistic nature in the way he engaged with the game -– all of these guys have broadened tennis.

"When it comes to on paper, I don't think you can argue against what Novak has done."