Djokovic, who was second best to Thiem when it came to mastering the gloom, wind and damp of Paris, was bidding to join Rod Laver in the Grand Slam history books.
He also played on Thursday while Spaniard Nadal played only on Tuesday and Friday and was able to put his feet up while Thiem slugged his way past Djokovic.
Thiem, who has never made it to the final at another Grand Slam, is looking to become the first Austrian to win a major since Thomas Muster lifted the Musketeers Cup at the French Open in 1995.
He even summoned the tour supervisor at one stage to complain about the severity of the conditions.More news: Almond OnePlus 7 Pro to be available in India on June 14
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"Being in the final of Roland Garros again means a lot and especially coming back from a tough situation with all the injuries that I had", said Nadal.
Spain's Rafael Nadal (R) hugs Switzerland's Roger Federer (L) after winning their men's singles semi-final match on day 13 of The Roland Garros 2019 French Open tennis tournament in Paris on June 7, 2019. A week after having to make way for Serena Williams in the main press conference room, the Austrian demonstrated his prowess on this surface by reaching his second successive final with an epic win over Novak Djokovic.
"He is the favorite, of course", Thiem said of Nadal. It's probably a little bit more hard to play these four hours with all the interruption than if you played in one time.
Despite playing over four hours over two days to defeat Djokovic for just the third time in 10 meetings, Thiem has only spent two more hours on court than Nadal getting to the final.
The Austrian is widely recognized as being an improved player from past year, and heads into the encounter ranked fourth in the world. "They looked at each other and said "OK".
Top seed Djokovic had been increasingly frustrated with the conditions on court with high winds kicking up the clay.
"I've been telling everyone - if someone wants to beat Thiem they have got to be ready for a big battle".