Mikel only made five appearances for the Blues before Mourinho was sacked and replaced by Guus Hiddink in December.
But he has become a regular under interim boss Hiddink and has missed just three games since the Dutchman took over at Stamford Bridge.
And Mikel believes he is now benefiting from having a manager who trusts him again.
“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 told Goal.
“Even if you do things right he would always make sure he finds fault.
“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.
