This victory also took his Grand Slam total to 18, only two behind 20, Roger Federer's haul.
His knees were still bothering him as he began his favourite season, the European clay court, which he has dominated.
The introduction of the Next Gen Finals tournament for the best players aged 21 and under was part of an effort to make stars of the up-and-coming generation, but the global appeal of Federer, Nadal and Djokovic will be impossible to replicate.
Corretja told Eurosport: "I have just spoken to Rafa and he looked very calm, he said it was crucial he broke back in the first set and got ahead".
"I don't know if it was her mistake or if it was only the mistake of the officials, but I don't know if she saw me or if she saw that somebody's in the room", he said after beating Gael Monfils to reach the last 16. And as everybody knows, I am not able to play so many weeks in a row like I did 10 years ago, eight years ago. So I have to do my schedule.
But in the past two years, he seems to have found a way to play well on grass again. When I first played here in 2005 I never thought I would be still playing here in 2019. He said: "I have had a very hard year with a lot of physical problems".
For the 12th time in his career, Rafael Nadal celebrated a title at Roland Garros.
"Of course, why not?" he said.
"He lost in the semi-final a year ago playing a great match". "I mean, if he wouldn't do that, for sure he wouldn't have that success every year in this tournament".
There has never been, and probably never will be a clay court maestro like Rafael Nadal in the world of tennis.
He has entered the tournament for the last three years only to pull out, and sensibly this year decided not to commit. "The experience says that having the right preparation, practising well, and maybe a couple of matches before there (works). But what he's been through these last couple of months is showing what a competitor he is and mentally that he's a genius". The would in play just as much as the baseline throughout the match.
The 32-year-old Djokovic, meanwhile, is stuck on 15, three behind Nadal, after falling agonisingly short of holding all four majors at the same time for the second time.
"I am not very anxious about this stuff", Nadal said. Just the numbers are insane.
Nadal might have won a 12th Roland Garros title on the weekend, but he remains well behind Djokovic, a semifinalist in Paris, in ATP rankings released Monday.
Thiem defeated Djokovic in the semi-finals in Paris while Stefanos Tsitsipas has been making rapid strides and beat Federer at the Australian Open.
"I was too negative". It would be awesome to get another chance next year, maybe against him or against anybody else. But I lost, I think, around 15 or even more Grand Slams in my career for injuries. "And I dropped a little bit towards the end of the first set". I think he has the possibility to win, and I want to hope that this year it will be possible.