Dominic Thiem beat Kevin Anderson for the first time in seven attempts to reach the Madrid Open final for the second successive year.
Later on Saturday, Germany's Alexander Zverev defeated Denis Shapovalov in the battle of the young guns to set up a showdown with Thiem.
Austrian sixth seed Thiem backed up his defeat of defending champion Rafael Nadal in the quarter-finals to beat South Africa's Kevin Anderson 6-4 6-2.
None of the their previous six meetings had been on clay and the surface proved decisive as Thiem managed to dictate against Anderson, who was appearing in his first semi-final of an ATP Masters 1000 event.
Thiem needed a single break of serve in the opening set and broke twice in the second to wrap up victory.
He said his victory over Nadal had been timely after being thrashed by the Spaniard in Monte Carlo and losing to him in the Barcelona quarter-finals.
"It gave me a huge boost of confidence, that's for sure," he said.
"But in the same time, it was a completely different match-up today.
"There was also the fact that I never beat him. It was 0-6 before today.
"Some things were a little bit shaky but I was keeping my level up from yesterday, so that was a great thing."
Thiem will need to maintain his level if he is to claim a first Masters 1000 title, although he boasts a 4-1 career head-to-head lead over Zverev.
The 21-year-old second seed Zverev was clinical as he trounced Canadian Shapovalov, two years his junior, 6-4 6-1 in less than an hour.
"It's obviously a great final for kind of the future ahead," Zverev said of the meeting with Thiem.
"We played five times against each other when he was already top 10 and I was more in the developing stage still. Obviously he's leading the head-to-head.
"But I'm playing quite well; so is he.
"Hopefully it will be another entertaining one."
The opening eight games went with serve but Zverev already has two Masters 1000 titles to his name and his greater experience told in the ninth game.
Shapovalov framed a forehand at 30-30 to offer the first break point of the match and Zverev pounced with a crunching backhand return his opponent fended into the net.
The second set proved a no-contest as Zverev took complete control against a dispirited-looking opponent.