Thiem has won 7-5 6-3 and lost creditably 7-6 6-4 in Madrid, and won 6-4 6-3 in Rome.
Nadal slides across the clay.
"Nadal is the first one to tell you he doesn't believe in tennis perfection", Courier said on ITV.
Nadal's form never wavered, though, and soon enough he was celebrating his 17th Grand Slam title overall, second among men only to Roger Federer's 20.
Thiem also beat Nadal in Argentina back in 2016.
Nadal's win-loss record at the French Open, his only two losses coming against Swede Robin Soderling in the fourth round in 2009 and against Djokovic in the quarterfinals in 2015. The Austrian won just one of the first nine points as Nadal immediately broke for 2-0.
Thiem dug in - especially in the roughly 13-minute sixth game - but he crumbled attempting to stay in the set, making four unforced errors. One down-the-line forehand victor landed right at the baseline and Thiem's shoulders sagged as he muttered to himself.
The problem for the 24-year-old was that his serve wasn't co-operating. "They are the first set is everything, and the weather is everything".
However, the 32-year-old remained in the ascendancy and passed up a further three break points before claiming the decisive break in the 10th game to take the lead.
A hold to love showed Thiem had not given up the ghost, however unlikely a repeat of Simona Halep's heroics from the same position a day earlier seemed. The two stars have combined to win the past six majors. Thiem makes his second double fault in the game.
The only thing that could stop Nadal now was surely an injury. So there was mild concern when Nadal called for the trainer midway through a game, requiring treatment on what looked like cramp in his hand.
The punishment continued, with Thiem by now looking up to his coach and shrugging as another forehand whistled past him.
This historical analysis doesn't lend itself to fancying Thiem's chances of denying Nadal an 11th French Open title this afternoon, and neither did my model pricing either.