"They call Mourinho the Special One, and I think he is," Ivanovic told Russian website Sport Express.
"If you win, his trust knows no bounds. He will make you fulfil the potential you were not even aware of.
"Training was unique under Mourinho. He sometimes plays mind games with the press, but when it comes to the most important things, the matches themselves, he is always very serious.
"If you want to play for Mourinho, you have to follow his demands.
"Mourinho helps to develop the best qualities -- professional and personal. You can't be indifferent to him. You either love him or hate him. That's what makes him special. I am glad that I had a chance to work with him.
"Ancelotti is very different. If players had a choice, I guess they would prefer to spend the entire career with Carlo.
"He is very calm and takes all the negative aspects on him, allowing the players to be comfortable. The results are equally good with both coaches."
Ivanovic ended a near-decade-long association with Chelsea to join Russian giants Zenit Saint Petersburg in January.