Djokovic's 6-3 6-2 3-6 6-2 victory on a sweltering, humid day in New York that left both players hunched over in the fourth set featured the world No. 1 playing a point with a ripped shirt and showman Monfils getting booed -- perhaps a first in his career -- for his antics.
Indeed, after much had been made about Monfils being more focused on court this year, his display in the first two sets could be considered a step backwards.
Djokovic will now take on Stan Wawrinka in the US Open final after Wawrinka won his semifinal match against Japan's Kei Nishikori 4-6 7-5 6-4 6-2.
Trailing 5-0 -- showing little of the play that got him to the last four without dropping a set -- Monfils walked into returns, coasted to the net and gave away shots. Djokovic lost his concentration, blowing three straight set points on serve at 5-1.
He was even forced to save break points at 5-3.
The pattern continued and sections of the crowd on Arthur Ashe stadium booed Monfils. Those boos intensified when he missed a forehand early in the third set and got even louder when he hit a double fault to drop serve.
Jean Gachassin, head of France's tennis federation and normally passionate in supporting French players, was left shaking his head in disbelief at Monfils' performance. On Twitter, 18-time grand slam winner Chris Evert criticized Monfils before his mini revival.
Djokovic, too, wasn't enamored with some of Monfils' actions.
"I thought at times that he was, you know, maybe behaving a little bit -- for some terms and judgments, unacceptable -- but, again, I guess that was part of his tactics," said Djokovic.
"He was five-love down with his game and he mixed it up. It seemed like it was a bit of a lack of effort, but then he started playing great. He started playing aggressive. He took chances. He came to the net."
Monfils -- now 0-13 against Djokovic -- felt he needed to do something different at 0-5.
"The guy is too good," Monfils said. "I just (had) to change. I think I'm gutsy to try that against the world No. 1. Five love, I show you that I play in a (non) academic way.
"I won't win a match like that but I can win maybe 15 minutes, two more games, one more game. I can push him a little bit to also defend myself ... and put him out of his balance.
"It was a great strategy, I think."
The crowd's venom woke Monfils up, however, and he won five straight games to lead 5-2. And when the 30-year-old raced to a drop shot and produced a cross-court winner, the fans roared their approval.
After squandering three straight break points with Monfils serving at 5-3, Djokovic tore his shirt -- and played another point.
Yet for Monfils, the damage had been done in the first two sets and he lost the final three games of the affair, which means France's men's grand slam title drought will extend to 34 years come the start of 2017.
"You cannot play that well coming into a semifinal and put in an effort like that for two sets," even with the stifling weather, former US Open finalist Greg Rusedski said on Eurosport.
Djokovic had become the first player to reach a grand slam semifinal benefiting from three retirements and/or walkovers, which he said helped him as he tries to recover from arm, wrist and shoulder injuries. But it's clear he is still struggling physically.
The trainer worked on Djokovic's serving shoulder; he hit just one ace -- in the first set -- and seven double faults.
But he is close to collecting a 13th major.