Djokovic has now won one more than rival Rafael Nadal (37).
"He has this software in his head that he can switch when a Grand Slam comes. Grand Slam is a different sport comparing to other tournaments. He switched his software," said Ivanisevic, a former Wimbledon champion.
"He's unbelievable, and he's still moving like a cat on the court. He's there. Like Ninja, he's everywhere."
"So it's fascinating to see, because sometimes you think, okay, now you have 23. But he's going to find, again, some kind of motivation to win 24, maybe 25, who knows where is the end."
On an historic day on Court Philippe Chatrier, Djokovic won his 21st consecutive Grand Slam tournament match to become the only man to capture each of the four majors - Australian Open, French Open, Wimbledon and US Open - at least three times.
The start of the clay season this year was not easy with the Serb having failed to win any event before his triumph in Paris.
"Coming to this tournament, he didn't come with unbelievable confidence and form. I was not worried. I said in Monte-Carlo, I don't count these tournaments. Only tournament that counts is this one," Ivanisevic, who became Djokovic's coach in 2019, said.
"The day we arrived here, he was better, he was more motivated, he was more hungry. Every day he played better and better... and today he just finished what we started actually in Monte-Carlo and now it's payday. We cash the check."
Djokovic, who dropped just two sets in the entire tournament, also beat top seed Carlos Alcaraz (20) in the semi-finals with the Spaniard suffering from cramps after two sets and with his game collapsing.
DEMANDING PLAYER
Winning Sunday's final was not easy, neither for the player nor for his coach.
"He chained us with handcuffs for three days," Ivanisevic said. "He's not an easy guy, let's put it this way. Especially when something's not going his way."
"But we are here to put our back and to get beaten. That's what the team is for."
"He was torturing us, taking our nails off. A lot of more things, but I cannot tell you that. But we are still here, we're alive. My heart is still okay. I'm an old man, I need to be careful of my heart," Ivanisevic joked.
Betting against Djokovic winning more majors should come with a warning, his coach said.
"Novak knows. Novak waits. Like (former player Andy) Roddick said, I read, he takes the legs, then he takes your soul, then he digs your grave and you have a funeral and you're dead. Bye-bye. Thank you for coming."
