The two remaining men's quarterfinals were suspended in progress and will resume Thursday.
Across the way at Court Suzanne Lenglen, No. 5 del Potro got distracted by a spectator right before a key double-fault, then marched over toward the stands to try to figure out who it was.
However, further rain came and the players had to leave the court again.
Nadal's match against Schwartzman was delayed by rain Wednesday with the Spaniard up 5-3 and serving ahead 30-15 in the second set after dropping the first, ending his streak of 37 consecutive sets won at the Paris event.
But those are not quite the same as the French Open, where Nadal is 86-2 for his career.
Bresnik knows, right along with everyone else, what a hard task it is to try to slow Nadal in a best-of-five-set match on his favorite surface and at his favorite tournament.
He was serving in the fourth game when he went back to his chair and unwrapped strapping on his left wrist.
He left Del Potro trailing in a cloud of Parisian clay dust to set up a final against Dominic Thiem on Sunday.
"Yeah, if I won the second set, I think is totally different the third set", he said. The final score was 4-6, 6-3, 6-2, 6-2 in Nadal's favour. Midway through the opening set, Nadal's aqua T-shirt was so soaked with sweat it stuck to him.More news: Trump, Kim co-star in U.S.-made summit film mixing propaganda, Hollywood
Schwartzman had the first advantage but dropped on a forehand shot.
A few hours earlier, as Nadal and Thiem warmed up, the booming voice of the announcer at Court Philippe Chatrier detailed the bona fides of both.
This will be the 10th tour-level encounter between Nadal and Thiem. He has won every final he has reached, and in those 11 finals he has dropped just six sets.
Nadal‚ a 16-time Grand Slam champion‚ claimed his 85th win in Paris against just two losses after weathering a big-hitting opening from 2009 US Open victor Del Potro to win 6-4‚ 6-1‚ 6-2.
"Even if it was 6-3 6-4, it was an uncomfortable match for me".
Top seed Simona Halep, twice a runner-up, takes on two-time major victor Angelique Kerber.
"I'm facing Rafa so I'm not the one who has the pressure", said Thiem. "If I play defensively and I don't take intensity, I will be lost".
"I know how to play against him", he said, without elaborating.
Halep is still chasing her first Grand Slam title.More news: Kim summit 'may not have happened without Otto Warmbier'
This included a quarter-final success in Madrid last month. Nadal's astonishing French Open record now reads: Won 85, lost two.
Stephens and Halep will face each other in the final in Paris on Saturday. This year, she was two points from defeat in the third round against Camila Giorgi of Italy before turning that match around.
Backed by fans who loudly chanted her first name between games, Halep went ahead 3-0 with the help of only one victor.
"There is a reason why he won 11 times here", said Thiem, a 24-year-old Austrian appearing in his first major final.
Nadal broke Thiem in his first service game to give the 10-time champion an early 2-0 lead in the first set.
"I have to play aggressively".
Muguruza, a two-time major champion, entered the semifinals having not lost a set in the tournament.
"He's playing with big confidence, winning the Lyon Open before Roland Garros and playing some great matches here".
Next up for Thiem is either Nadal, who is eyeing his 11th French Open title, or Juan Martin del Potro of Argentina.More news: Julen Lopetegui to Real Madrid is a surprise, says Guillem Balague