Nadal is looking to win his 11th French Open and is favourite to beat Belgian Dominic Thiem.
But Paris, to tweak the title of Ernest Hemingway's famous love letter to the city, has been a predictable feast for Nadal.
Del Potro missed six break points in the opener, including three at 4-4.
"That's why the guy was dominating clay-court tennis the last 14 years like no one else before and nobody ever will". Thiem has 13 career wins over top-10 players, and three of those victories have come this year.
"Just thinking in a positive way and just thinking that I have to hold".
Nadal has already established himself as one of the five greatest men's tennis players in history. For sure he is beatable, but you have to have the level, and Dominic has the level and you have to play the flawless match and the most important thing is you can't miss the occasions that you have.
The tournament favorite served out his 450th Tour-level match on clay to reach his 24th Grand Slam final, Del Potro drilling a backhand return long to crash out. "It was very hard to stop that", Nadal told reporters. However, after the game, Nadal revealed that he was struggling against Del Potro in the first set.More news: Trump predicts ‘tremendous success’ for historic summit
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Nadal broke in the lone game he had an opportunity to wrap up the set. Nadal's coach, Carlos Moya, told a small group of reporters it is something to be aware of but not to fixate on: "Not too much focus, otherwise it can get in your head and it's not helping". However, I'm going to be aggressive and have a small bet on Thiem winning 3-0, now available at around [20.00]. Faltering even slightly "is not something that is happening very often with him, but the way he's been playing the last three sets yesterday and the last two sets today, is gonna help his confidence".
It was the Austrian's third consecutive appearance in the semifinals at Roland Garros. The most recent meeting was in this years Rome Masters, a match Thiem won in straight sets.
At the age of 25 Marco Cecchinato finally got a taste of what it's like to win matches at a Grand Slam tournament and after his unexpected run to the French Open semi-finals, the Italian is determined to prove that he is no one-hit wonder.
Nadal is bidding to become only the second player to win 11 titles at any Grand Slam tournament after Margaret Court, who won the Australian women's singles title 11 times.
Thiem had five set points, three of which he squandered very early, while Cecchinato had three of his own.
"The big key was the second set, it was a close tiebreak and if I lost it, I didn't want that because it would be a tough match", said Thiem. "And Nadal has been doing it for years and years and years". He is in the age of improvement. Thiem will have to produce tremendous quality and depth for hours to have a chance to join Soderling and Djokovic's exclusive club. Facing a rampaging Rafael Nadal on clay is a threat any day, but on the terre battue of Court Philippe Chatrier is akin to running with the bulls.