Jiri Lehecka has warned his giant-killing run at the Australian Open is "not over" after booking a spot in the quarter-finals with a stunning upset of Canadian star Felix Auger-Aliassime.
The unseeded Czech fought back from a set down and held his nerve in the deciding tiebreaker to complete a shock 4-6 6-3 7-6 (7-2) 7-6 (7-3) victory over the sixth seed on Sunday.
"Honestly, it feels amazing," Lehecka said.
"It's tough for me to find some words because what we've been through last year (losing in the first round) and now coming back to Australia, if somebody had told me before the tournament that I would play like this, I wouldn't believe him.
"I'm super happy that I'm through and, yeah, excited."
World No.71 Lehecka had never previously won a match at a grand slam in four attempts.
But the 21-year-old has now knocked out seeded rivals Borna Coric (21), Cameron Norrie (11) and Auger-Aliassime, as well as American wildcard Christopher Eubanks.
Next, he takes on third seed Stefanos Tsitsipas, who outlasted Jannik Sinner 6-4 6-4 3-6 4-6 6-3 in a gruelling four-hour battle.
"The run is not over," Lehecka said.
"All the guys I beat over here, all of them are incredible players.
"I must have played my best tennis and showed all the cards to beat them.
"Coric in the first round, Eubanks in the second round and then Norrie and now Felix, I mean, it sounds crazy but it's true.
"I'm very happy and so excited to continue the journey."
Karen Khachanov is also through to the quarter-finals, having continued his grand slam renaissance with a straight-sets mauling of Yoshihito Nishioka.
Khachanov won the first 14 games of the match en route to a 6-0 6-0 7-6 (7-4) victory over the Japanese 31st seed.
"First two sets I didn't know what was going on but it's never easy when you are going with a score too easy," the world No.20 said.
"You feel it and then at one point Yoshi tried to turn it around, he pumped the crowd and it's normal.
"So I tried to stay focused all the match from the beginning but it's not easy to win with this score, three straight sets. So the third set was a really tough one."
The quarter-final conqueror of Nick Kyrgios at last year's US Open, Khachanov has rediscovered the form that thrust him into the world's top 10 four years ago.
With 15 aces and 30 winners, the big-serving Russian ultimately needed less than two hours to progress and book a last-eight clash on Tuesday with rising American Sebastian Korda.
Korda knocked out 10th seed Hubert Hurkacz in a five-set thriller, prevailing 3-6 6-3 6-2 1-6 7-6 (10-7).
It was the fifth match in the men's tournament decided by a fifth-set tiebreaker.
Korda rattled off six straight points during the tiebreaker to build a 7-3 lead but lost the next four points as Hurkacz levelled.
The 29th seed eventually closed it out on his own serve, later revealing an unusual secret to his success throughout the rollercoaster finish.
"I got a little superstitious with the towel. The towel got me through it," he said.
"Every time I went to the towel, I won the point. So I just kept going to it."
The win propelled Korda into his first grand slam quarter-final and franked the 22-year-old's form after a straight-sets triumph over seventh seed Daniil Medvedev in the third round.