Thiem also has momentum on his side, having won their last meeting at the Madrid Open. His appetite was audible in the long, trailing groans of effort that echoed around the old concrete stadium. I know I have to play my best tennis to have a chance on Sunday. "He's a player that can be adapted more to the clay, it will be tough". Monte Carlo, Barcelona and Rome fell at his feet again, with just that single blip in Madrid.
The world number one is still the overwhelming favorite to pick up his 11th French Open title, but former victor Mats Wilander thinks Juan Martin del Potro, Nadal's semi-final opponent could cause him some troubles.
Nadal's backhand was doing most of the damage, with three winners having set up the double break on his way to a two-set lead, and Del Potro was broken to love in his first serve game of the third, with Nadal inflicting a devastating backhand victor up the flank after another majestic defence. Thiem had five set points, three of which he squandered very early, while Cecchinato had three of his own.
On his favorite tennis court, Rafael Nadal was struggling on Friday. He gave Nadal a sound beating in Madrid, and whilst that has never been Nadal's favourite tournament - with suggestions that the relative altitude makes the ball travel faster through the air, dulling Nadal's usual advantages on clay - I'm inclined to view it as a sign of a growing equality on clay between the two of them. "It was very hard to stop that", Nadal told reporters.
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.
A fourth set point for Thiem vanished because of one of Cecchinato's many drop shots. 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". "I'll try my best and hopefully do better than past year".
This time, Thiem faced Cecchinato, a 25-year-old from Sicily who never had won a Grand Slam match until this tournament and was the lowest-ranked men's semifinalist at the clay-court major in 19 years.
It was the Austrian's third consecutive appearance in the semifinals at Roland Garros.
Serving for the match Del Potro was given an easy ride as Cilic blazed three backhands in succession long.
That win, according to three-times former champion Mats Wilander, should be all Thiem is thinking about when he prepares for Sunday's clash.
The semi final victory over Juan Martin del Potro was marred by the Argentine needing to request his physiotherapist come onto the court to evaluate a hip injury.
Thiem will be keen to emulate Thomas Muster, the only Austrian man to reach, and win, the final at the French Open, back in 1995. Of players under 29, only Thiem and Milos Raonic have reached major singles finals: Raonic lost in the 2016 Wimbledon final to Andy Murray. He is in the age of improvement.
He did not look unduly affected though and his heavy groundstrokes took a toll on Nadal who rescued three more break points in the ninth game.
Yet Nadal, whose all-time claycourt record now stands at 414-36 says nobody should assume his feats are routine and that each victory is celebrated like the first.