The 20-year-old Mensik hit 20 aces en route to beating veteran Pablo Carreño Busta, 7-5, 6-4, then Jaume Munar won his first Davis Cup singles for Spain by defeating No. 17 Jiri Lehecka 6-3, 6-4.
Spain hadn’t reached the semifinals since its sixth title in 2019, while the fourth-seeded Czechs had missed out since 2014.
Top-ranked Italy, seeking a third straight title and fourth overall, faces Belgium in the other semifinal. The Italians are without world No. 2 Jannik Sinner, who is resting.
The Davis Cup Finals in Bologna is the sixth edition of the revamped event that crowns a champion at a neutral site.
