With Djokovic leading their US Open semifinal 5-0, an uninspired Monfils began hitting exceptionally casual returns, which clearly irked Djokovic, who saw four set points evaporate.
"I've seen strategy changes," ESPN analyst John McEnroe said on the broadcast, "but this tops everything. Even Sigmund Freud above couldn't figure this out.
"This is bordering on unprofessional. The only reason I'm saying borderline is because it's working."
Only to a point, because Monfils eventually lost the chaotic and disjointed match 6-3, 6-2, 3-6, 6-2 on Friday in Arthur Ashe Stadium.
Djokovic will next face No. 3 Stan Wawrinka, who made his way into the final later Friday night by defeating No. 6 Kei Nishikori 4-6, 7-5, 6-4, 6-2.
In head-to-head play, Djokovic leads Wawrinka 19-3. However, Wawrinka's biggest win as a professional came over Djokovic last year in the French Open final, and Wawrinka has won his past 10 finals in a row.
"I'm really excited," Wawrinka said in his on-court interview. "I watched the final so many times here. Roger [Federer] and Novak are great champions. To play in the final against him is going to be special.
"Hopefully, I'm going to be ready."
In classic Muhammad Ali rope-a-dope fashion, Monfils turned would-be tanking into a tactic. He created a distraction, then rushed into the void left by Djokovic's waning concentration.
It happened again in the third set, when Monfils' quirky behavior drove Djokovic to tear off his shirt after the final point.
Afterward, Monfils answered McEnroe's charges.
"I'm sorry if you think I'm unprofessional, but I guess I'm working, I'm learning," Monfils said. "I think I'm failing, for sure, a lot, but I try to stand up. It's tough, because when he calls me unprofessional, he calls my coach unprofessional, calls my physio unprofessional -- all my team, actually, unprofessional.
"I have nothing personal [against] him, so I'm very sad to heard that. I'm very sad to learn that such a legend criticized me, because at the end what I can say to John is, 'I want to be the best.'"
Both Monfils and Djokovic cramped significantly in the fourth set and called for visits from the ATP trainer amid the hot and humid conditions.
"At times in decisive, tense moments, we had many exchanges form the baseline," Djokovic said in his on-court interview. "Gael is very entertaining to watch, a very charismatic guy. I do sincerely hope all you guys enjoyed our battle today."
Djokovic stopped short of criticizing Monfils' style of play.
Monfils finished with 11 double faults and 52 unforced errors.
Djokovic benefited from three injured opponents: Jiri Vesely (withdrew), Mikhail Youzhny (retired) and Jo-Wilfried Tsonga (retired).
After defeating Monfils, Djokovic has played only 13 sets and a total of 118 games. This puts him on a record pace for fewest sets and games in an Open-era major that featured a 128-man draw and only best-of-five-set matches.
Wawrinka has played a staggering 23 sets and 237 games.
And what prompted Djokovic to tear of his shirt?
"I keep asking myself the same question," he said, laughing. "Sometimes you don't have answer. Sometimes it just happens in the heat of the moment."
And how did he bounce back from that?
"The way I bounce back from that," he said, "is take another T-shirt from my bag. I already feel better."
Djokovic ousts Monfils in four sets to reach final
Novak Djokovic takes down Gael Monfils 6-3, 6-2, 3-6, 6-2 to advance to the final of the US Open.