The Italy international's move to AC Milan was completed on transfer deadline day.
Lee told BBC Radio Five Live's Sportsweek: "I think it is the right move.
"He is a talented player with a lot of ability. But the biggest disappointment for me was that he played at the expense of his team-mates.
"He would stop the game and do a few tricks, or do this, that and the other. You could never rely on him.
"If you have a player and he has one or two faults, you can work on them and eradicate them. But this guy has too many, I think.
"(City manager) Roberto Mancini has treated him like a father would at times, and he was always wishing and hoping that this guy was going to do it. But to be quite honest, he has done it on very few occasions."