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.
Alcaraz overcame rolling his right ankle in the second set and hoped to be fully fit for Sunday's final against second seed Sinner.
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.
World number 10 Sinner defeated Alcaraz in four sets in the last-16 at Wimbledon before going on to surrender a two sets lead to lose to eventual champion Novak Djokovic in the quarter-finals.
"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."