However, Nadal has won both their clashes at Roland Garros - in 2014 and in last year's semi-finals by a comfortable 6-3, 6-4, 6-0 margin.
Another feature was his ridiculously slow play when serving, nearly always over the 25-second limit and sometimes going well into the thirties.
The top seed went 2-0 ahead in the second set as he wore Thiem down in lung-burning rallies, leaving the Austrian screaming in frustration.
A glimmer of hope was when the middle finger on his left hand started to cramp in the middle of the fourth game, causing him to take a salt tablet and have the strapping on his forearm to be removed, which is there to stop the sweat pouring onto his palms.
He bagged the second set when Thiem sent a backhand long. But against an opponent of Nadal's caliber, a lack of variance in his game plan proved crippling. He already defeated great players, such as Djokovic and Goffin after being on the verge of elimination in the first round. Across the other slow-medium clay venues - Monte Carlo, Barcelona and here - Nadal has utterly schooled Thiem.
Federer's 11 are at Wimbledon, and if Nadal beats Thiem on Sunday, he'll keep his flawless French final mark; he's never lost in the ultimate match at this event.
Thiem was still on the back foot in the third set, being forced to save four break points in the first game.
However, during the treatment Nadal revealed that he was concerned about whether he was going to be able to continue. He converted the second to make the score 2-1.
Thiem was considered the stiffest test for Nadal at the French Open and understandably so.
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.
Nadal won his sixth French Open title by defeating Federer once more in Paris.
In contrast, there are eight women now younger than 28 who have been Grand Slam singles finalists.
A remarkable year ended when the world No 1 completed a career Grand Slam by beating Novak Djokovic at Flushing Meadows.
And in 2012, he surpassed Borg's record to become the most successful player in French Open history with his seventh crown. He's the only player to beat Nadal on clay in the past two years - in Rome last year and in Madrid last month.
Rafael Nadal is set to play for his 17th grand slam tournament title. The finals take place on Saturday and Sunday afternoon after 2 PM GMT.