'Can't believe it': Australian Open rocked by 'horrible' Dominic Thiem drama

Tennis fans have been left stunned after reigning US Open champion Dominic Thiem was sent packing from the Australian Open in straight sets.

Thiem, who made it to the final at last year's Australian Open against Novak Djokovic, fell short of the quarter finals thanks to a 6-4 6-4 6-0 defeat at the hands of Grigor Dimitrov.

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Dimitrov hustled to a surprise two-set lead over a listless-looking Thiem and cruised through the final set in just 21 minutes to win 6-4 6-4 6-0.

"Throughout every season you have one of those matches where you just keep the ball rolling and I think today was just one of those days where I was entirely trying to focus on what I was doing," Dimitrov said.

"I think he might have actually struggled with something but I want to give myself credit."

While Dimitrov's victory set him up for a quarter-final clash with qualifier Aslan Karatsev, who advanced to the quarter finals thanks to an unlikely and historic upset of his own, Thiem's fans were left to ponder exactly why he had struggled so badly against Dimitrov.

Thiem had only two days to recover from his epic five-set comeback against Australian star Nick Kyrgios, but fans were nonetheless stunned by the one-sided showing.

Thiem snared an early break against Dimitrov before the Bulgarian responded by breaking Thiem twice to come from behind and claim the first set.

The second set was a similar affair, with Thiem again drawing the first break and an early lead before dropping two of his own service games as Dimitrov took control.

Thiem looked a shadow of himself in the third and final set, with a brilliant Dimitrov closing out the match in style.

The 18th seed will play unheralded Russian Aslan Karatsev in the quarter-finals and was wary of what the qualifier presented.

"If you're here, it's for a reason - there's no doubt about it," Dimitrov said.

"Whether it's a fairytale or not, it's a match - you've got to be ready."

Dimitrov to face Australian Open qualifier Aslan Karatsev

Unheralded qualifier Aslan Karatsev will head into an Australian Open quarter-final clash with Grigor Dimitrov high on confidence as he looks to add another chapter to his extraordinary grand slam debut.

Two days after seeing off eighth seed Diego Schwartzman, Karatsev fought back from two sets down to outlast 20th-seeded Canadian Felix Auger-Aliassime 3-6 1-6 6-3 6-3 6-4.

Ranked No.114, the Russian will now face 18th seed Dimitrov, who progressed to the quarter-final with a brilliant 6-4 6-4 6-0 victory over third seed Dominic Thiem.

Karatsev had earlier been nonplussed when asked which of those two high-profile players he preferred to face - understandably, given his earlier scalps.

"I'll be ready for everyone," he said.

With his fourth-round win, he became the lowest-ranked man to reach the final eight at Melbourne Park since Patrick McEnroe in 1991, when the American was also ranked 114.

Karatsev had fallen short in nine previous attempts at qualifying for a grand slam before breaking through in Doha last month.

With AAP

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