The 'Big Three' dominated men's tennis over the last two decades with a collective 66 Grand Slam titles between them but Djokovic is now clear of the retired Federer (20 slams) and Nadal (22), who is expected to call time on his career next year.
"He's a winner," former Wimbledon champion Ivanisevic told reporters. "He's the guy who is motivating himself.
"He had luck to have guys like Nadal and Federer, they came before him, so they pushed each other.
"When you tell him he can't do something, it's even worse. Then he's going to show you that he can do it. No excuses. He always tries to find a way to win, to fight, even when he's not feeling well, injured, not injured."
Ivanisevic, who has been coaching Djokovic since 2019, said he considered the Serb's US Open triumph - which put him level with Margaret Court with the most major singles titles - as "the biggest achievement in sporting history".
The 51-year-old added that he was not surprised by Djokovic's hunger.
"He's just enjoying, he likes the challenges. Like you ask me 25 (majors), yeah, if he wins 25 he's going to think, 'If I win 25, why not 26?' It's always one more, something more," Ivanisevic said.
"He's taking care of his body, he's taking care of everything, every single detail has to be perfect, prepared. He's never happy on the court.
"I don't know if that's good or bad, not good for us," he said smiling.
