He is the only man to beat the world number one on clay in the last two years - in Madrid this spring and in Rome last year.
Nadal crushed de Potro in straight sets, 6-4, 6-1, 6-2.
In yesterday's delayed matches from Wednesday, Rafa Nadal completed his fightback over Diego Schwartzman, recovering from a set and break down to eventually ease through in four sets, while Marin Cilic succumbed to Juan Martin Del Potro, with the Argentine progressing also via a 3-1 scoreline, albeit in four rather tighter sets.
The No. 1-ranked Nadal compiled a 35-20 edge in winners while making only 19 unforced errors today.
"He is tall so Rafa's shots don't bounce over his shoulder, he has big weapons, the serve which gives him free points and the forehand which is the biggest in the game and he can hit through Nadal's forehand with it".
"After the first rain delay, the match changed a lot because I played more aggressive with high intensity and things were more on my side", Nadal said.
From the moment Nadal took the second set, it looked unlikely Schwartzman would earn a first win in six attempts against the man at whose academy he had trained.
It was the 24-year-old Austrian's third consecutive appearance in the semifinals at Roland Garros. I had three surgeries on my left wrist.
"It was not a very nice feeling", Thiem told the Court Philippe Chatrier crowd afterward.
Paris: Juan Martin del Potro believes it's virtually impossible to defeat Rafael Nadal on clay and backed the Spaniard to claim an 11th French Open title in Sunday's final against Dominic Thiem. He played some wonderful aggressive tennis to get through Djokovic in the quarters, just like he played awesome aggressive tennis to get to the quarters.
It was a different story on Thursday as Nadal won 12 of the first 13 points before cruising into the last four. Basically, it's typical Nadal in the French Open.
One of those was a 6-3, 6-4, 6-0 rout in the Roland Garros semi-finals 12 months ago. He is 110-2 in all best-of-five matches on red clay.
"He's [Nadal] a big favorite against everybody", said Thiem.
They have not played on clay for 11 years, however, so it will be a step into the unknown on Friday.
"But I have a plan".
Thiem has been to the semifinals in Paris three years in a row.
Rafael Nadal admits that his desire to clinch an 11th French Open title on Sunday is fired by his growing realisation that the end of his career may not be too far away.
The No. 7-seeded Thiem reached the first Grand Slam final of his career by ending the surprising run of 72nd-ranked Marco Cecchinato of Italy at Roland Garros with a powerful performance in a 7-5, 7-6 (10), 6-1 victory Friday. That's the goal.' Analyzing the match won over the Argentinian, Nadal added: 'I feel lucky to have saved the first set.
He put out seeded players Pablo Carreno Busta and David Goffin before the seismic shock of knocking out 2016 champion Djokovic in the quarter-finals.