The Brazilian was a regular fixture for the Blues under Mourinho, but he found himself frozen out of the starting XI by caretaker Guus Hiddink.
Ramires eventually joined Chinese side Jiangsu Suning in January.
He told Goal: "I always had a very good relationship with Mourinho, so much so that the things became complicated for me at the club when he left.
"I remember he wanted to count on me since he was at Real Madrid and it was a pleasure to work together with him. Mourinho's CV speaks for itself.
"He has won many important titles and proved that he is one of the best at what he does."
"With us he was always a calm guy, but on the pitch and in training he demands a lot of us, which I do not see as being a problem. It was in this way of working that he became what he is today.
"I did not see any problem [to explain Chelsea's dismal 2015-16 campaign]. Football can be like that. We were champions the previous season, but then things did not work out. It's hard to explain. It was practically the same team."