Lorenzo Musetti stunned world No 3 Alexander Zverev to reach the semifinals in Vienna on Friday, describing his comeback triumph as "a pretty big win".
Italian 17th-ranked Musetti came through 2-6, 7-6 (7/5), 6-4 after two hours, 36 minutes to see off the 2021 champion.
"It didn't start how we planned, I was struggling to find the right balance with my forehand and the variation of my backhand," said the 22-year-old who was an Olympic bronze medallist in the summer, just weeks after reaching the Wimbledon semifinals.
"It's a pretty big win because Sascha really loves to play here, on this court, in these conditions. But, after the first round, I was feeling in good shape and today I showed that."
Musetti will next face world number 18 Jack Draper after the Briton defeated Tomas Machac of the Czech Republic in his quarterfinal 6-3, 3-6, 6-1.
"I thought the first set was really physical. It's always tough playing Tomas, he's so solid off the ground," said Draper after booking his place in an eighth tour semifinal.