"As long as Rafa is healthy, it will be very hard to beat him here", del Potro said on Friday.
If Nadal's march toward an 11th championship at Roland Garros was going to be stopped on this day, things were going to have to go del Potro's way right then.
"If I want to beat him, I have to play that way like I did in Rome and in Madrid", Thiem said. "I know he's a great player".
'I hope to be ready to do it.
Nadal, who already has more titles at a single Grand Slam than any men's player in history with his 10 French Open wins, can collect his 17th career major with a win Sunday.
Rafael Nadal held serve in the opening game against Juan Martin del Potro in their French Open semifinal. However, Nadal later revealed that he was "suffering" against the Gentle Giant in the first set of the match.
"For me, the motivation to play here always is high, high as possible".
That is not to say Dominic Thiem's time will come - it will, after knocking on the door for the last two years reaching the semi-finals, this is the next progressive step.
In 2016, Nadal won two straight-set matches, then withdrew before the third round because of an injured left wrist.
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'He's a big favourite against everybody, ' Thiem said after his straight sets win over Marco Cecchinato.
Thiem had three set points at 6-3 but Cecchinato quashed them all and reversed a triple of set points in his favor, but he couldn't convert a tiebreaker win this time as Thiem moved ahead after two errors.
Young pretender - and perhaps heir to the throne - Dominic Thiem has been dubbed the Prince of Clay and he will get a shot at the undisputed ruler of the Parisian land for more than a decade.
At the press conference following the game, Nadal was asked what "biological age" he was at after a study which showed Real Madrid superstar Cristiano Ronaldo was just 23 (the footballer is actually ten years older than that).
The 24-year-old Thiem was the last player to get the better of Nadal, too, last month at the Madrid Open.
Surely, so did del Potro.
And the first set was indeed tight, even with del Potro calling for the trainer at 2-3.
Thiem had to weather three set points for Cecchinato, at 7-6, 9-8 and 10-9.
Ah, but there's a reason Nadal is 11-0 in semifinals at the French Open, a reason he is 10-0 in finals there - so far.
Last year, Nadal completed a "Decima" in Paris, lifting the trophy without dropping a set and losing just 35 games in total.
"That was definitely the key", Cecchinato said.