Dominic Thiem beat qualifier Sebastian Ofner 6-2, 3-6, 6-3 to advance to the quarter-finals of the Generali Open on Wednesday.
The 2020 US Open champion has been down twice in the deciding set and saved two break points when serving for the match before taking down his compatriot Austrian.
Thiem, 28, who returned in March with a long-term wrist injury, has reached at least the quarter-finals in the last three tournaments he has played in, including Bastad and Gstaad.
The former world No. 3 who won the 2019 clay court tournament will take on Yannick Hanfmann after the German beat Ivan Gakhov 6-3, 6-7(5), 6-4.
The three seeded Spaniards have entered the last eight by winning their second-round matches in straight sets.
Third seed Roberto Bautista Agut eliminated Austrian Yuri Rodionov with a wild card 6-1, 6-4, fifth seed Albert Ramos-Vinolas defeated Juan Pablo Varillas of Peru 6-3, 6-4, and seventh seed Pedro Martinez beat Federico. Korea defeated Argentina 6-4, 6-3
The other two seeded players were eliminated.
Fourth-placed Aslan Karatsev of Russia was edged out by Dusan Lajović of Serbia 7-5, 6-3, while Czech player Jiří Lehecka upset eighth seed Joao Sousa of Portugal 7-6 (6), 1-6, 6-3.
Another Spaniard, unseeded Pablo Andujar, lost to Austrian Filip Misolich 6-4, 6-0.