The 10-time champion lost the first set 6-4 to the impressive Argentine Wednesday, but returned under sunny skies Thursday to win the next three sets 6-3 6-2 6-2 to reach the French Open semifinals.
"It is nearly impossible to beat Rafa", said Del Potro who had his chances but failed to convert any of his seven break points before his challenge petered out into tired hopelessness.
With the two heavy favourites in the semi-finals winning, we have the final that most people during the latter stages would have wanted, Nadal v Thiem, and before I discuss the data in detail, I wanted to talk about their previous meetings a little more.
"I think it helps, definitely, knowing that you were the last guy to beat him", said Bresnik, whose association with Thiem spans more than 15 years.
"I know I have to give a little more than I have given until now in this tournament".
"I think that was my chance of the match", Del Potro said of the ninth game.
Thiem, one of the most consistent performers on clay court over the last three seasons, conceded he is under a lot of pressure ahead of his first Grand Slam final, in which he will face the 10-time champion and Rafael Nadal.
In this picture, Spain's Nadal celebrates after victory over Argentina's Diego Schwartzman during their men's singles quarter-final match on day twelve of The Roland Garros 2018 French Open tennis tournament in Paris, June 7, 2018. I have been on court just couple of minutes ago.
Nadal raced away with 14 of the last 17 games. 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. He then went on to beat Nadal in straight sets in Madrid and seemed on course for a first Masters title before collapsing to Alexander Zverev in the finals and then losing to Fabio Fognini in the first round of the next Masters in Rome. 'I can't give him the game.
Brandon: Thiem has looked invincible throughout Roland Garros 2018 and looks likely to reach his first Grand Slam final as he takes on Cecchinato in the semis.
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But Thiem has shown himself to be the biggest threat to Nadal's utter dominance on his favoured surface and he's the only player to beat him over the past two years.
Of that set, Thiem said: "If I had lost it, it would have been a very close match".
Nadal has won six of his nine matches against Thiem, all of them coming on that famously hard red clay.
"He's too strong", Del Potro said.
Conditions will play a huge rule in Thiem's chances.
As for what sort of tactics will be employed Sunday, Nadal's coach, Carlos Moya, offered a hint.
The 37-set run was Nadal's longest at the French Open. Cecchinato was accused of match-fixing and suspended for 18 months in 2016, but he appealed, and his punishment was dropped on a technicality.
Thiem had to weather three set points for Cecchinato, at 7-6, 9-8 and 10-9. Thiem may well even take a set. Then Thiem got to 10-all with a drop shot of his own.
"It's his court, he has the keys and he has to take advantage of that", said Moya, referring to Nadal's track record at Philippe Chatrier stadium.