"Jose and I had rows," he told the Daily Mail. "If I wasn't in the team, I would speak to him about it and sometimes there would be an explosion and we would be enemies. I think that's normal in football. But we were friends again the next day.
"He is a great manager and, along with Guus Hiddink, the best I have ever worked with. When I said I felt I needed to move on, he understood. He did not stand in my way. He appreciated how difficult I found being on the bench after being a big star at PSV and how much I wanted to play regularly."
Kezman was stunned when Mourinho left earlier this season and even more surprised when Grant was swiftly appointed as his replacement.
"I know the background," he said. "I understand that Mourinho had problems with the owner. But the manager that they have now does not have Mourinho's qualities. When Mourinho was there, Chelsea was like a machine. Everything ran like clockwork.
"Now, talking to old friends at the club, I understand it's not so good. There are rows on the training pitch, the kind of problems that never would have happened when Mourinho was in charge. Chelsea are still a strong team. Just look at their position in the league. But it is a good time to play them."