The new Nigeria captain made just five Premier League appearances under the Portuguese coach this season, but has become a mainstay in the side under Guus Hiddink.
And Mikel believes he is benefitting from having a manager who trusts him again, suggesting Mourinho overlooked him regardless of how well he performed in training.
“I think confidence is everything, if a manager doesn’t believe in you, trust me there’s no way you can succeed,” the 28-year-old exclusively told Goal while on international duty with the Super Eagles.
“Even if you do things right he would always make sure he finds fault.”
He continued: “People change in any walk of life, maybe he decided he wanted to do better in a different way and he didn’t need me anymore.
“He didn’t have the belief that he had in me before, which is fine because every manager has the player that they have trust in.
“It is a tough business, football, so when a manager comes in he wants to have people he believes in. If he doesn’t believe in you he doesn’t play you. And I think it’s all about a manager giving a player confidence.”
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Chelsea technical director Michael Emenolo described a “palpable discord” between the manager and the players prior to Mourinho’s departure, when the side languished in 16th place – just one point above the drop zone.
Mikel has previously credited new boss Hiddink with reinstalling a sense of togetherness at Stamford Bridge, and praised the impact the Dutchman has made in such a short space of time.
“Hiddink came in, he spoke to me, he gave me the confidence and now I have played 20 games and we’re in the best position - where we haven’t been all season.”
This is not the first time Mikel has aimed a jibe at his former boss, with the Nigeria international claiming in January that there was a total lack of communication between himself and Mourinho, something Hiddink has changed dramatically.