Top seed Pablo Carreno Busta and fellow Spaniard Jaume Munar will meet in the Andalucia Open final on Sunday.
Carreno Busta was pushed all the way by Albert Ramos-Vinolas in a pulsating semi-final, ultimately coming through 6-1 3-6 7-6 (7-5).
"It was so close. I don't know what happened in the second set," Carreno said. "At the beginning of the match, I was very focussed on my game and being aggressive.
"After that, Albert, of course, started to push [back] more and [I] started to lose my level a little bit.
"I just kept fighting all the time, and I want to thank everyone [in the crowd] for their support. This is what we missed last year, the crowd. It's very important to play these kinds of very close matches with a crowd like this."
PCB survives ARV! @pablocarreno91— Tennis TV (@TennisTV) April 10, 2021
He will take on Munar after the 23-year-old edged past Carlos Alcaraz 7-6 (7-4) 6-4.
Munar, who reached a final on the ATP Challenger Tour last week, said: "I feel happy and excited. I've been working a lot during the last [few] months.
"It's a gift for me to be here in a final, and especially in Marbella which is one of my favourite places. I feel excited."
Elsewhere, Lorenzo Sonego is aiming to become the first Italian to win an ATP Tour clay-court title on home soil for 15 years when he takes on Laslo Djere in the final of the Sardegna Open on Sunday.
Sonego, 25, overcame American Taylor Fritz 6-4 5-7 6-1 to give himself the opportunity to add to his Antalya Open title from 2019.
Standing in his way is Serbian Djere, who cruised past Nikoloz Basilashvili 6-2 6-0 in just 52 minutes.
Djere was in control from the outset and from 3-2 in the first set went on to win nine straight games, helping him to his third ATP Tour final.