Tennis great Rod Laver suggested Saturday that engravers could start putting Novak Djokovic's initials on the Australian Open trophy, with something "miraculous" needed to prevent him winning an 11th title.

Laver, the only player to twice win all four singles Grand Slams in the same calendar year, called the Serbian superstar "amazing" and admitted he would be shocked if anyone beat him.

"He has all the shots, he knows exactly when he can play them, when he can't play them," the 85-year-old told Australian media after arriving at the tournament from his California home.

"He's priming himself to get through to the final."

Laver, who has the centre court at the Australian Open named after him, added that Djokovic's athletic prowess and tennis brain set him apart from everyone else.

"It almost unfolds in front of him, what he should be doing. He's a great champion," said the Australian 11-time Grand Slam winner.

"He serves well. His ground strokes are unbeatable.

"I have to believe unless someone miraculously plays their best tennis to knock him off, they can start putting part of his initials on the trophy now."

Should Djokovic do as Laver expects, he will win a 25th Grand Slam to surpass Margaret Court's all-time record.

The 36-year-old dropped sets in his opening two matches at Melbourne Park, when he said he was under the weather.

But he was back on form to coast into a fourth-round meeting with French 20th seed Adrian Mannarino.