Top seed Alexander Zverev battled back from a set down to beat Argentina's Francisco Cerundolo and book a spot in the semifinals of the Munich ATP tournament on Friday.
The three-time Munich champion won 5-7, 6-0, 6-2 and will take on Italy's Flavio Cobolli on Saturday.
Zverev burst out of the blocks and served for a 5-1 lead in the opening set but appeared to suddenly lose his rhythm, winning just one more game as Cerundolo powered back to take the opening set.
As the second set began, and with the support of the home crowd, the 28-year-old found his form as swiftly as he had lost it, bouncing back to win the final two sets while dropping just two games.
The German came into Friday's match holding a 4-3 career advantage over the fifth-seeded Cerundolo but had never previously beaten the Argentine in three matches on clay.
Reigning champion Zverev, whose most recent title came in Munich a year ago, is chasing a record fourth triumph at the tournament, having also won in 2017 and 2018.
Earlier on Friday, Cobolli was the first to book a spot in the final four after he defeated Czech Vit Kopriva 6-3, 6-2.
Playing on his favourite surface, the fourth seed won the opening set and cruised to a 5-1 lead in the second. He missed two match points on Kopriva's serve before finishing it off in the following game.
Later on Friday, American second seed Ben Shelton faces Brazilian teenager Joao Fonseca while Denis Shapovalov takes on Alex Molcan.