Thiem had too much, though, battling to take the first two sets and then cruising through the third to earn his shot at the title.
And the world No. 8 wasted no time in racing away with the decisive third set to book his place against Nadal in his first grand-slam final. "But I'm also aware that here it's tougher", said Thiem, the first Austrian in a major final since Thomas Muster won in Paris in 1995.
"You have to be focussed and keep your passion for the game".
"I have to find it inside me and find the right options for Sunday, the options that will be the right ones to succeed".
At least Thiem can boast being the only man to have defeated Nadal on clay in the last two years.
Thiem, 24, is seeking to win his first grand slam title in his debut appearance in a major final, and the Austrian seventh seed has been in impressive form throughout the two weeks in Paris.
But the Spaniard was impressive on Friday, finishing with 35 winners and 19 unforced errors to Del Potro's analysis of 20 and 32. 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.
"I was a bit lucky", said Nadal, who is 10-0 in French Open semi-finals and 10-0 in finals at the tournament. Both played superbly - and both had chances to end it. Thiem went ahead 6-3, but wasted three set points there, including a bad volley into the net at 6-4 that left him chewing ruefully on his left index finger. The tall Argentine created six break point opportunities on the Mallorcan's serve, and faced none on his own in the first nine games. For sure he is beatable, but you have to have the level, and Dominic has the level and you have to play the ideal match and the most important thing is you can't miss the occasions that you have.More news: Cristiano Ronaldo's plan amid Real Madrid exit rumours involves Manchester United
Nadal did not have almost as hard a time against the fifth-seeded del Potro. I had a lot of break points.
Rafael Nadal held serve in the opening game against Juan Martin del Potro in their French Open semifinal. I mean, Dominic beat Rafa in Madrid.
Despite some spirited resistance, the 11th seed couldn't live with Nadal's new-found intensity and revamped strategy, and the 16-time grand slam champion sealed the victory for the loss of only four games with his fourth match point. "He deserved to win". "This is why the guy was dominating clay-court tennis over the last 14 years like nobody else before".
Injuries have hindered the Spaniard's Wimbledon campaigns in recent years but assuming he comes through Sunday's final unscathed he could yet mount an assault on the All England Club title he has won twice before.
He believes he has a particularly powerful weapon on his side - breakfast. And I spoke to Dominic on Friday, and he made it clear to me that best-of-five at Roland Garros is so very different from best-of-three in Madrid.
"That was not a nice feeling".
Cecchinato, who was banned for match-fixing in 2016, had never won a match in the French Open prior to this year's edition.
"Today, all day, on Philippe Chatrier, the fans said, "Forza, Marco", so this is the best moment for me", he added.