Grigor Dimitrov ended third seed Stefanos Tsitsipas' Vienna Open hopes with a battling last-16 win on Thursday.
Tsitsipas, who took Novak Djokovic to five sets in the French Open semi-finals this month, had come from behind to beat Jan-Lennard Struff in his opener in Austria but was this time on the wrong end of a fightback.
The Greek edged the first set after a tie-break but failed to convert either of his break points in a 6-7 (5-7) 6-4 6-3 reverse.
It was Dimitrov who prevailed after two hours and 14 minutes for his first top-10 win of the season, securing a quarter-final against Dan Evans.
"It's never easy to come out of a situation like that," Dimitrov said. "I was focused, but he went for it.
"In the tie-break a few close calls here and there went his way. [There was] not much else I could have done, I felt. But I kept on believing and kept on doing the right things.
"I stayed in the match, which I think was the most important thing. He's such a great competitor. You always have to be ready. I was just focusing on the most simple things of the game."
The other seeds found life a little easier on Thursday, with Dominic Thiem and Andrey Rublev each through to face one another.
Reigning champion Thiem brushed aside Cristian Garin in straight sets, while Rublev was granted a walkover as Jannik Sinner succumbed to a foot injury early in their meeting.
Daniil Medvedev also advanced but needed three sets after dropping the first to Vasek Pospisil.
Djokovic was not in action, meanwhile, but learned the identity of his Friday quarter-final opponent as Lorenzo Sonego reached the last eight.