Romania's Simona Halep returns the ball to Spain's Garbine Muguruza during their women's singles semi-final match on day twelve of The Roland Garros 2018 French Open tennis tournament in Paris on June 7, 2018.
"I was not able to move the hand, the finger", Nadal said.
A fourth set point for Thiem vanished because of one of Cecchinato's many drop shots.
"And if he would have won the tiebreak, he would be full power, for sure, in the third set".
An 86th win on Sunday will give the 32-year-old Spaniard an 11th French Open title - a joint record for triumphs at a single Grand Slam along with Margaret Court who won 11 Australian Open trophies, albeit not all in the professional era.
Thiem beat Marco Cecchinato 7-5, 7-6, 6-1 in his semifinal matchup.
Nadal raced away with 14 of the last 17 games.
The second set tie-break proved to be decisive as the Italian player squandered three set points, having recovered from a 6-3 deficit, reports Efe.
Nadal dealt with that ultimately minor inconvenience and claimed his record-extending 11th French Open championship Sunday by displaying his foe-rattling excellence in a 6-4, 6-3, 6-2 victory over No. 7 seed Dominic Thiem.
"He's a big favourite against everybody", Thiem said.
Nadal is now just the second man to reach 11 finals at the same Slam‚ equalling Roger Federer's mark at Wimbledon.
The world number one held serious discussions with coach Carlos Moyá in an intense session in the heat as he studiously went about his business.
But those are not quite the same as the French Open, where Nadal is 86-2 for his career.
Nadal lost the opening set 6-4, and went on to trail by 2-3 in the second on Wednesday when the match was spoiled by rain.
"The first set was very hard, there were lots of opportunities for Juan Martin del Potro and I was perhaps a little lucky to win it", Nadal said afterwards.
Thiem is the only player to beat Nadal on red clay over the past two seasons.
Truth is, there were not many the rest of the way, as Nadal finished with 35 winners and just 19 unforced errors.
It rarely is for Nadal at a place he has lorded over the way no other man ever has at any Grand Slam tournament. You don't get to a Grand Slam semi-final by accident.
Easing through the third set, Thiem became only the second Austrian player to reach the final of Ronald Garros, following in the footsteps of Thomas Muster, who won the title in 1995.
After breaking Nadal's serve to take the ninth game, Schwartzman hit a forehand victor at 40-30 to take the first set 6-4. "When (Thiem) is dominating the point, he is very risky".
Although at times during the first set against Del Potro, especially when he was 0-40 down at 1-1 and 15-40 down at 4-4 it looked as though he might be in for a real scrap.
The Argentine has never beaten Nadal on clay.
Thiem led 6-3 but suddenly lost focus.
Del Potro, the US Open victor in 2009, is playing the tournament for only the second time since 2012 after a spate of injuries.