Defending champion Carlos Alcaraz survived a worrying ankle injury scare to beat Giulio Zeppieri and set-up an Umag final showdown against Jannik Sinner, the man who ended his Wimbledon hopes.
The 19-year-old, who will reach a career high four in the world next week, triumphed 7-5, 4-6, 6-3 against world number 168 Zeppieri of Italy in a gruelling semi-final on the Croatian clay courts.
The final will be Alcaraz's 100th tour-level match.
"It's amazing to be in a final here again. I enjoy playing here in Umag," said the Spaniard.
"At the moment the ankle is good. I don't feel too much right now. Let's see tonight or tomorrow morning, but I am going to say I will be ready for the final.
He added: "It would be amazing in my 100th match to get the win, and of course it is amazing to be No. 4 on Monday. It's something great for me, but right now I am just focussed on the final."
Sinner reached his first final of the year by knocking out fellow Italian, qualifier Franco Agamenone, 6-1, 6-3.
"The final will be very tough. Everyone was expecting this matchup," said Sinner.
"Today I played quite well. Also Carlos is playing well. I'll try to play some good tennis. I have to raise my level if I want to win, so I will try to prepare in the best possible way."
