Nadal is looking to extend his mind-boggling record of Roland Garros titles to 12, while Thiem is aiming for his first Grand Slam title. This year's final is also a rematch of last year's championship, which Nadal won in straight sets. And then there's the added wrinkle of Thiem coming off a five-set victory over Novak Djokovic that extended over two days and didn't finish until Saturday due to inclement weather.
How both players react to those factors will go a long way to determining this year's champion. Our experts answer the biggest questions and break down what to expect in Sunday's final.
Due to the quick turnaround for Thiem, how much will rest play a part in Sunday's final?
ESPN.com tennis writer Peter Bodo: Ordinarily, it might not be too huge a factor because of the degree of diligence Thiem brings to his fitness training. But this is Nadal he's facing. The No. 2 seed is well rested, and his stock in trade for a dozen years has been grinding and breaking down opponents patiently, implacably and inexorably. Nobody -- nobody -- sustains a comparably high level of intensity from the first point to the last, taking breathing room away from his opponent. That will play on Thiem's mind from the get-go, and only loom larger in a close match.
ESPN.com contributor Simon Cambers: It has to be a factor, and Nadal must have allowed himself a smile as Thiem and Djokovic went five sets. That's a big advantage to Nadal, who hardly needs an edge in Roland Garros finals. The one good thing is that it might take the pressure off Thiem, who can swing freely.
ESPN senior writer Bonnie D. Ford: There was a lot of social media chatter about Nadal sitting around watching the Djokovic-Thiem semifinal in sweats, licking his chops. I personally think he prepares for the Roland Garros final with the same level of professionalism no matter who he's playing or how long he's had off. Thiem is eight years younger, and it's not as if he played five hours in broiling heat the day before; Thiem's drawn-out, interrupted semifinal match required more episodic energy and an imperviousness to annoyance. I think the final will be a quality match if the weather cooperates.
What is the most concerning factor for each player going into the match?
Bodo: Simple answer for Thiem: stamina. Thiem is one of just four men with three or more wins over Nadal on clay (Thiem is 4-7 against Nadal on the surface), but none of those four wins has been in a best-of-five match. It doesn't help that Thiem was forced to play more than two hours of demanding tennis Saturday due to the suspension of his Friday semifinal against Djokovic. Thiem's physical reserves are bound to be lower than when he lost to Nadal in last year's final.
Nadal, meanwhile, has to worry about two things, starting with his physical fitness. In the past nine months alone, he issued a walkover to Roger Federer before their semifinal meeting at Indian Wells and retired during his US Open semifinal against Juan Martin del Potro. You never really know his condition. The other source of worry: Thiem is one of the few players who can hit through Nadal on any surface. At 25, Thiem is eight years younger. His body is more durable. His emotional reserves might be sufficient to trump his fatigue after that supercharged win over Djokovic.
Cambers: For Nadal, it's the power, speed and belief of Thiem's game. The Austrian has been here before, and although it was Nadal who beat him, the nerves should not be so severe. For Thiem, it's Nadal -- the history, the aura, the man himself. And Nadal's game, which seems to be close to its best.
Ford: Thiem nailed it when he said self-belief -- corny but true. Assuming the weird weather continues, Nadal will have to adjust to variable conditions with the same skill he did against Federer, and be just as focused on the big points.
Thiem believes he can win it all. What does he have to do to actually get there?
Bodo: Everyone, including Nadal, is susceptible to pressure. The defending champion will be facing more pressure from the start, given that he's the "King of Clay" and -- for a change -- facing a finalist who has never won a major. One way to make Nadal feel that pressure acutely is by keeping him from building an early lead. To do that, Thiem must seize every opportunity that presents itself. Thiem blasted his way to 15 break-point opportunities in his semifinal win but converted just six. He has to be a little more effective on crucial points, stick a high percentage of first serves into play, and avoid engaging in long rallies from well behind the baseline.
Cambers: Thiem has to go for his shots, stick to his game plan and never deviate. He has to mix up his serve, maybe with some serve and volley if Nadal stands deep on returns. And Thiem must try to get the crowd on his side, because any little thing might help.
Ford: Disrupt Nadal's game with varying pace, be aggressive and avoid getting into baseline punching matches.
How is each player different from a year ago?
Bodo: Nadal is a year older at a time when every year counts, at least for players not named Federer. Nadal had a great 2018 until he retired from the US Open. He did not return until January at the Australian Open, where Djokovic exposed the rust in the final with a comprehensive victory. Nadal had a less successful clay season than in past years, but given the way he has played at Roland Garros these two weeks, you can throw that right out the window.
Since Nadal overpowered Thiem in straight sets in last year's final, the Austrian baseliner has won his first Masters event (at Indian Wells) and solidified his status as perhaps the second-best clay-court player, behind Nadal. Thiem has added a little more variety to his game, and he has clearly benefited from a coaching change after a slow start this year. He was just 3-4 in February when he hired Chilean Olympic gold medalist Nicolas Massu. Since then, Thiem has accumulated a 19-4 record. His confidence must be sky high, even if his reserves are low.
Cambers: Nadal is probably in the same kind of situation he was 12 months ago. Winning in Rome last month gave him the confidence he needed, and he seems to have improved through the fortnight in Paris. The difference for Thiem is that this year, he really believes he can win a Grand Slam. He is a man who continues to improve every year -- and if he has a chance, he might be ready to take it.
Ford: Small but possibly significant factors: Thiem has been to this dance before now. He beat Nadal in Barcelona in April. Nadal looked more vulnerable on clay than he has in his non-injured recent past.
What is your prediction for the final?
Bodo: It's difficult enough to beat Nadal when you're well rested, but the unfortunate circumstances created by the rain on Friday and Saturday suggest that Thiem is anything but. It would take a monumental letdown by Nadal -- or an otherworldly effort by Thiem -- to block a victory by Nadal. He'll take it in four sets.
Cambers: I can't see anything other than a Nadal win. He's peaking at the right time, and with the extra rest, everything is in his favor.
Ford: Nadal in four sets.