Dominic Thiem had all the answers against Gael Monfils in the Australian Open fourth round. AFP/VNA Photo

MELBOURNE - World number five Dominic Thiem swatted aside an error-prone Gael Monfils to book a maiden Australian Open quarter-final on Monday, with the Frenchman resorting to an underarm serve in desperation.

The two-time Roland Garros finalist proved too wily for his experienced opponent, crushing him 6-2, 6-4, 6-4 on Rod Laver Arena.

It set up a last-eight showdown with either world number one Rafael Nadal or temperamental Australian Nick Kyrgios, who play later.

Thiem has long had the measure of Monfils, winning all five of their previous encounters, and the 10th seed had no answers on a hot Melbourne day, making 32 unforced errors.

"I played my best match so far, I had a good feeling," said Thiem, the first player from Austria to reach the last eight at Melbourne Park since Stefan Koubek in 2002.

"But the score looks much easier than the match was. I always play my best tennis against Gael."

Monfils is a nine-time Grand Slam quarter-finalist but only one of them came in Melbourne and he never looked like reaching a second.

The Austrian, targeting a maiden Grand Slam crown, went a break up for 2-1 in the opening set and then grabbed another as Monfils struggled to deal with Thiem's accurate and varied first serve.

With Thiem pressing hard again in the second set, Monfils tried an underarm serve at 40-30 in game three. It worked, catching the Austrian off-guard.

But it only delayed the inevitable. With Monfils appearing to struggle in the heat, Thiem created four break points in game seven and the Frenchman finally succumbed by missing an easy net volley.

The third set followed a similar pattern with Thiem breaking early and quickly completing a routine victory. AFP