Jiri Lehecka had not anticipated still being in the Australian Open at this point but his latest victory against a seeded player saw him advance to the quarter-finals on Sunday.
The Czech youngster produced another impressive showing to beat number six seed Felix Auger-Aliassime 4-6 6-3 7-6 (7-2) 7-6 (7-3) in the fourth round.
Despite having never won a main draw match at a grand slam prior to this tournament, Lehecka has now defeated three seeds, having also dispatched of Borna Coric (21) and Cameron Norrie (11) during his passage to the last eight.
"Honestly, it feels amazing," he said after the victory. "To be in the quarters, I wouldn't believe it if somebody told me this when I was on my way over here.
"I'm super excited for everything that will come next. Of course, I'll try to do my best to recover well and to show my best tennis again in my next match."
While his Canadian opponent utilised his serve well, hitting 20 aces, it was on net points where Lehecka thrived, winning 33 of 41 while Auger-Aliassime managed just 11 of 26.
The 21-year-old has another big test next as he faces third seed Stefanos Tsitsipas, having lost to the Greek in their one previous meeting in Rotterdam in February despite winning the first set.
"I'll be super excited [to face Tsitsipas]," Lehecka said. "I will go for that revenge, for sure. I know that he will remember how we played last year in Rotterdam. One set I was the better player on the court. Then he overtook the match. But I think that he will remember, and he will know what my strengths are.
"He will feel that I can get him under pressure. At the same time, I know that he's a great player. I mean, he's number four in the world.
"I know how to play against him."