Jiri Lehecka, seeded 21st, advanced to the biggest ATP final of his rising career when he routed 28th seed Arthur Fils 6-2 6-2 on Friday (Saturday AEDT) at Hard Rock Stadium.
Lehecka's countryman Jakub Mensik won the tournament last year.
"Today was a great match," Lehecka said.
"Definitely brought me a lot of confidence going into the Sunday final. I must say that it was one of the better matches that I played in my life."
The 24-year-old will make his first appearance in an ATP Masters 1000 decider and faces world No.2 Jannik Sinner after the Italian beat fourth seed Alexander Zverev 6-3 7-6 (7-4).
Sinner sat out the event a year ago as he served a three-month suspension after testing positive for a banned substance.
Now he's on the verge of winning a second Miami Open title in three years and becoming the first male to win the 'Sunshine Double' since Roger Federer in 2017.
Sinner, who served 15 aces, has beaten German Zverev seven straight times and won a record 32 straight sets at an ATP Masters 1000. A hardcourt dynamo, Sinner topped Daniel Medvedev in the Indian Wells final on March 15.
Sinner, 24, has a 3-0 career record against Lehecka, beating him last at the 2025 French Open.
Lehecka broke Fils in the opening game and the outcome never seemed in doubt. On match point Lehecka served an ace, one of six for the contest. He didn't serve a double fault, nor face a break point in his semi, and hasn't been broken in the tournament.
Fils, the 21-year-old Frenchman, had saved four match points in his quarter-final victory over American Tommy Paul but seemed to have little gas left. Fils had won their last meeting on February 19 in the quarters of the Qatar Open in Doha, 6-3 6-3.