Alex de Minaur has maintained his perfect record at the Australian Open against lower-ranked opponents, outlasting big-hitting Serbian Hamad Medjedovic to advance to the third round.

After being stunned by the world No.90 in the first set, de Minaur’s superior fitness and class came to the fore as he prevailed 6-7 (7-5) 6-2 6-2 6-1 in three hours and four minutes on Rod Laver Arena on Wednesday night.

It puts the 26-year-old through to the third round at Melbourne Park for the sixth consecutive year.

De Minaur will likely meet American 29th seed Frances Tiafoe in the round of 32, who was on track to beat Argentine Francisco Comesana.

Australia’s world No.6 boasts a perfect 18-from-18 record against lower-ranked rivals in Melbourne. But he didn’t have it all his own way against the powerful Medjedovic.

“I weathered the storm,” de Minaur said.

“He (Medjedovic) was playing some unbelievable tennis, serving great, hitting the ball from the baseline, really big and deep, and not really allowing me to do much.

“Ultimately, a five-set match is a long match, so there’s going to be lots of chances.

“I took them, and I’m super happy to battle my way through.”

When de Minaur rolled through the second set in 42 minutes, organisers inexplicably didn’t shut the centre court roof before heavy rain arrived. The wet weather forced play to be suspended for half an hour while the court was mopped up and the roof was closed.

But the extended break failed to halt de Minaur’s momentum, with Medjedovic immediately dropping serve.

After he reaching the third round at Roland Garros last year, this was the fiery Medjedovic’s first appearance in the main draw of the Australian Open.

The 22-year-old defeated Argentine Mariano Navone in the first round to book his clash with de Minaur.

After a potential next match against Tiafoe, who he has beaten in three of their four previous encounters, de Minaur’s opponents following that could be 10th seed Alexander Bublik (fourth round) and world No.1 Carlos Alcaraz (quarter-finals).

-AAP