Third seed Dominic Thiem became the biggest casualty of the Australian Open so far with a meek defeat by Grigor Dimitrov in the fourth round.

Thiem battled back from two sets down to beat Nick Kyrgios on Friday and it appeared that effort had taken it out of the Austrian, who led Novak Djokovic by two sets to one in the final in Melbourne last year before winning his first grand slam title at the US Open.

This match could not have been more different to Friday’s clash, which was played in a raucous atmosphere, and the empty stadium matched Thiem’s demeanour as he slumped to a 6-4 6-4 6-0 loss.

Thiem cited “some little physical issues” but said: “I don’t want to find any excuses. But the thing is that I’m also not a machine.

“I mean, sometimes I would like to be, but there are really, really bad days. As soon as you’re not 100 per cent there on the court on this level, then results like this come up, and that’s exactly what happened today.”

Dimitrov certainly played his part, staying extremely solid and taking full advantage of his opponent’s struggles and he has eased through to a fourth quarter-final in Melbourne.

The 29-year-old said: “The way that I came through, and especially in that first set, also being able to stay really focused and really dedicated to the game that I wanted to apply, it was something that I think I did very well today.

“Clearly maybe he was struggling a little bit in the third set or not, but I think I did all the necessary to keep a steady play.”

There, the Bulgarian will play this week’s surprise package, qualifier Aslan Karatsev, who continued his remarkable run with a 3-6 1-6 6-3 6-3 6-4 victory over 20th seed Felix Auger-Aliassime.

At 27, Russian Karatsev has spent his whole career in the lower reaches of the sport, never breaking the top 100 or playing in the main draw of a grand slam until this week.

He is the first debutant to reach the quarter-finals of the men’s singles at a slam since Alex Radulescu at Wimbledon in 1996 and the first qualifier to make the last eight in a decade.

Dimitrov will certainly not be taking the outcome for granted, saying: “It takes time for everyone to get to somewhere, but the best part is that you treat every player the same way, and I will treat this match with no difference.

“Clearly in order for him to be here he’s done something right, and he’s playing great tennis right now. Of course he’s a dangerous player.”

For Karatsev, this is reward for years of toil away from the spotlight, and he said: “I was working a lot and it just happened right now. It’s like you never know when it happens. It just happened here.”

Twenty-year-old Auger-Aliassime is one of the most exciting young talents in men’s tennis and this will surely be a tough defeat to get over.

The young Canadian believes it will prove to be a valuable experience, though, saying: “It’s really a shame that I couldn’t get through today. It’s difficult to swallow, but it’s tennis, that’s how it is, life, and honestly it can only help me in the future.

“It’s the first time I played five sets, first time this happens to me – maybe not the last one, we’ll see. But I’ll just try to learn from that and be better next time.”