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The Australian wasn't at his best in the first set, but still managed to clinch it as Moutet missed several opportunities to turn the screw on the No.7 seed, and descended into a bad mood as a result.

Moutet, who stunned Daniil Medvedev in the previous round, was warned for smashing his racquet in frustration and completely lost his cool for large parts of the second set as De Minaur showed no mercy and raced to a 4-0 lead.

But the Australian was unable to achieve a shutout as Moutet started to find his feet, giving himself ironic praise as he claimed the fifth and sixth games of the set, and earning a break back as De Minaur inexplicably coughed up a double fault.

But it was a rare error for De Minaur, who took his 34th win of the year on a Moutet double fault, claiming his 21st win on hard courts, more than any other player on the ATP Tour so far this year.

"It wasn't pretty tennis by any means," De Minaur said after the match.

"I knew it was going to be a battle, it was going to be a tricky match with not a lot of rhythm, because that's just what he's [Moutet] able to do to opponents.

"I just had the mentality to do whatever I needed to do to give myself a title match tomorrow."