Dominic Thiem's run at the Winston-Salem Open came to a halt as Jack Draper claimed a comfortable straight sets victory on Wednesday.
In the first meeting between Draper and Thiem, it was the 20-year-old Brit who sealed his place in the last eight with a routine 6-1 6-4 victory.
Draper charged ahead in the first set, creating five chances to break and taking two of them, while his sole successfully converted break point in the second set paved the way for the Winston-Salem debutant to serve out the match.
World number 55 Draper has now reached three Tour-level quarter-finals this season, while 2020 US Open champion Thiem had been on a run of making it to the last eight in his last three tournaments, in Bastad, Gstaad (where he made the semis) and Kitzbuhel.
Draper did not offer up a single break opportunity, and said: "I was really good behind serve, really solid. In the second set it was tough because he was coming up with some amazing shots. It was a real honour to be on court with Dominic. He's an amazing player.
"I started confidently, I started well. I was hitting through the ball, felt good in the conditions. It was a difficult start because I felt like everyone was supporting Dominic and I knew that I needed to come out confidently and sharp, and that's what I did."
Draper will meet Marc-Andrea Huesler in the quarter-finals, after the world number 102 overcame Ilya Ivashka.
Botic van de Zandschulp is the favourite after Grigor Dimitrov's retirement due to illness with the Dutchman progressing to the last eight by defeating Spain's Jaume Munar in straight sets. He will face Benjamin Bonzi after the Frenchman's 7-5 6-2 defeat of Thiago Monteiro.
Maxime Cressy will face Adrian Mannarino after coming from a set down to beat Lorenzo Sonego 6-7 (4-7) 6-2 7-6 (7-3), while Richard Gasquet and Laslo Djere make up the other quarter-final tie after respective victories over Steve Johnson and Jason Kubler.