Nadal's match against the fifth-seeded del Potro on Friday will mark his third consecutive day of competition, though the 10-time Roland Garros champion isn't fazed by the extra work.
Seventh seed Thiem, 24, resisted fightbacks from the world No.72 in the opening two sets of their semi-final on Friday.
There's also the emotional toll to consider - after beating Cilic, Del Potro broke down in tears on court and said: "It's tough to speak now".
The fourth set was a foregone conclusion nearly before it began, and Schwartzman was only able to win two games as his impressive 2018 French Open came to an end.
Thiem is the only player to beat Nadal on red clay over the past two seasons.
While Thiem faces an nearly impossible task on Sunday, Nadal was taking nothing for granted against the man who beat him in Madrid.
World 72 Cecchinato had knocked out three seeded players to reach the semi-finals, including 12-time major victor Novak Djokovic in the quarter-finals.
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Klay Thompson, who did not score in the first half, scored 10 points to lead Golden State to an 86-65 lead after three quarters. As they have all season, the Warriors used an overwhelming third quarter to clinched the win.
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California's unusual primary system allows the top two primary candidates to advance to the general election, regardless of party. From the primary results in California, it seems likely the Democrats are further than ever from capturing the House.
With that being said, Thiem is on the upswing of his career.
Thiem went for the jugular in the third set and after racing to a 4-0 lead in double quick, he finished off the job to reach his first Grand Slam final.
The second set turned into a tight tactical battle with neither able to break serve.
"The big key was the second set", he said.
The Spaniard followed up a backhand passing victor with another victor from the forehand to earn two break points, and then drew the error on the second to snatch the first set in the blink of an eye.
Del Potro claimed the tiebreaker, and though he faltered late in the second set, he regained control of the match with five straight wins to claim the third.
"When I missed that volley it wasn't a very nice feeling".
-When you buy Tennis Channel Plus, your 12-month subscription gets you access to every ATP Masters 1000 tournament played outside the USA, and every round through the finals of WTA Indian Wells, Miami and Cincinnati. "But after the loss, I went a little bit down mentally".
In 2016, Cecchinato was accused of match-fixing and suspended for 18 months, but he appealed, and his punishment was dropped on a technicality.
Croatian Cilic played an very bad game when serving for the set but he was gifted another chance to serve for the set after breaking del Potro again and at the second time of asking he levelled the match. Then Thiem got to 10-all with a drop shot of his own.