The Austrian fifth seed swept into the Australian Open quarter-finals for the first time after a straight-sets demolition job on Frenchman Gael Monfils on Monday at Rod Laver Arena.

Thiem had never before passed the fourth round at Melbourne Park but rolled past world No.10 Monfils 6-2 6-4 6-4.

Thiem will play the winner of Monday night's clash clash between Nick Kyrgios and world No.1 Rafael Nadal.

The 26-year-old confirmed to on-court interviewer Jim Courier that his mother Karin had started a new tradition last year in getting a tattoo for each tournament he won.

After making the vow, Thiem had a career-best campaign, winning five titles, with an eagle feather for his victory in Indian Wells and a panda for saluting in Beijing among the tattoo haul.

With his mother watching on in the stands, Thiem was asked what kind of tattoo she would get if he won the Open, he replied: "For sure, a kangaroo".

The victory stretched Thiem's all-time dominance over Monfils to 6-0 but the Austrian said it was tougher than it looked.

Thiem rated it as his best performance of the tournament."I think that I played my best match so far at this Australian Open, but very, very good feeling," Thiem said.

"The score looks way easier than the match was. "I think I was lucky to make an early break in each set and then was managing to hold my serve well well and I'm so happy because I am for the first time in the quarter-finals here."

Thiem's charge comes after splitting with Austrian great Thomas Muster after just two weeks together.

Courier said during the match that there was "tension" between the pair.

"I can repeat a quote that Thomas Muster gave to an outlet saying that sometimes you see a house from the outside, it looks beautiful, but you don't know what it is really like until you get inside."

So there seems to be a little bit of tension there in that relationship."

However, Thiem said there was no bad blood with the former French Open champion but the relationship just didn't work out.

"Nothing bad happened there - we already said before we started the relationship that if it doesn't work out, we're going stop it, and that was the case.

"I think it's way more relaxed than everybody thinks."

Australian Associated Press