Nadal will face either Novak Djokovic or Matteo Berrettini for a place in Sunday's final, where he will bid to win a record 21st Grand Slam.
The win was far from straightforward as the Spaniard found himself in trouble on his service games throughout the first three sets. In fact, at one stage in the third set, it seemed as though Schwartzman could do the unthinkable and take a second set off the Spaniard in Paris.
But the Mallorcan had other ideas and raised his level when he needed to, eventually prevailing in four sets.
On that note, here are three key takeaways from Nadal's win:
#1 Rafael Nadal is not infallible at Roland Garros
Rafael Nadal lost just a single set against Diego Schwartzman but could very well have lost another. Schwartzman had a few half chances in the third set but could not capitalize on them.
Nadal's serve and forehand completely disappeared towards the end of the second set, allowing Schwartzman to gain a foothold in the contest.
The Argentine ultimately did not have enough firepower to subdue Nadal, but the likes of Alexander Zverev, Novak Djokovic and Stefanos Tsitsipas will be capable of pouncing on any opportunities the Spaniard offers up.
#2 Rafael Nadal still has the ability to explode into life
Rafael Nadal's movement was not at its best in the initial stages of the match, but he took things up several notches when he really needed to in the closing stages of the third set. With the score at 4-4 in the third, Nadal became a completely different player and blew Diego Schwartzman off the court.
The World No. 3 not only moved quickly but he also struck the ball with a lot more venom. Nadal ended up reeling off 30 of the last 35 points played in the match to show exactly why he is the greatest claycourter of all time.
#3 Rafael Nadal must improve his serve in the rounds to come
Rafael Nadal's serve deserted him in the second set as he allowed the Argentine to claw his way back into the match. Nadal only managed to land 59% of his first serves in the second set and was broken twice.
The Spaniard clocked an average speed of 114 mph on his first delivery and 93 mph on the second in the set that he conceded. In a bid to regain accuracy on his serve, Nadal dropped those speeds to 111 mph and 91 mph, respectively in the third.
That was enough to give the Mallorcan more control as he landed a whopping 88% of his first serves in the third set.
However, Nadal cannot afford to take pace off his serve when he comes up against the likes of Novak Djokovic, Alexander Zverev and Stefanos Tsitsipas, who will be only to happy to pile the pressure on the Spaniard.