But an 85-2 win-loss record like Nadal's in Paris is not something easy to shake.
Croatian Cilic played an very bad game when serving for the set but he was gifted another chance to serve for the set after breaking del Potro again and at the second time of asking he levelled the match. His appetite was audible in the long, trailing groans of effort that echoed around the old concrete stadium.
Del Potro said the Austrian, the only player to beat Nadal on clay over the past two seasons, has a chance - albeit a slim one. I'm happy to play the final again at my favourite grand slam. "He's a player that can be adapted more to the clay, it will be tough".
Nadal has dropped only one set so far in reaching the final - one more than he conceded in winning the 2017 title. "Best of five is also different story". "Of course, the rain helped stop the match and helped me think about the match, and that's a reality".
Charmingly, despite Nadal's accomplishments, he's still prone to nerves when he steps on center court here.
Nadal seldom leaves the door cracked very long.
Nadal crushed del Potro's spirit with the intensity of his tennis in the second set, bounding 5-0 ahead before the Argentine registered a game to lift the spirits of his fans.
Belgium 3-0 Egypt
Meanwhile, Salah's agent took to Twitter to deny reports claiming that representatives had offered the player to Barcelona. The Beigium forward said he hopes Salah will recover from the injury in time to make a big impact at the World Cup .
"I think that was my chance of the match", del Potro said of the break points he held at 4-all in the opening set of Nadal's 6-4, 6-1, 6-2 blitz.
These two have played nine times and Nadal has won six of those matches.
Relentless Nadal broke to love at the start of the third, and as he moved on to match point an exhausted Del Potro paused for breath, bent double, as if he had been punched in the stomach.
The Spaniard was a set and a break down on Thursday morning before he regrouped and blazed through the last two sets on Friday morning (AEST) in a last-eight showdown played over two days due to rain.
There have, however, appeared to be one or two chinks in his armour at Roland Garros this year. The most recent meeting was in this years Rome Masters, a match Thiem won in straight sets.
Nadal is only the second man after Roger Federer to reach 11 finals at the same Grand Slam.
Friday will be the second time Nadal and Del Potro meet at Roland Garros.
Thiem weathered three set points for Cecchinato, at 7-6, 9-8 and 10-9. The Italian succumbed quickly in the third set, sparing the French Open from a final in which his past match-fixing case would have been rehashed under a global spotlight. However, Thiem was the better player in the big moments. "He's improving every year".
The key was the opening phase of play at the mid-day restart on Court Philippe Chatrier.