Umag - Uruguay qualifier Pablo Cuevas has upset sixth-seeded Andreas Seppi 6-3, 6-1 to make the Croatia Open quarter-finals on Thursday.
Cuevas, held serve, played patiently from the baseline, and pushed Seppi into unforced errors.
Seppi failed to convert three break points while trailing 5-3 in the first set and never recovered.
He won the first game of the second set, then lost the next six, winning only four points on Cuevas' serve.
Cuevas won his maiden ATP title in Bastad, Sweden, 10 days ago.
The last qualifier to reach the quarter-finals in Umag was Victor Troicki of Serbia in 2007.