Ancelotti said: "The reason is that when he moved to Chelsea from Milan that is a hard thing to do. He had to move to another country and the environment changed.
"All these factors obviously affected his condition. He's trying to play the way he can. I believe we have seen many times that he has great talent. If he overcomes these problems, which are mostly psychological and because he moved to a different country, then he will achieve a lot at Chelsea."
Ancelotti also ruled out a return to the San Siro for Shevchenko while a Chelsea spokesman confirmed a groin operation during the summer is the reason why he is behind his team-mates in terms of preparation for the season ahead.