Mancini made the claim when discussing City's inexperience in the Champions League.
The Etihad boss said: "We're a good team, but we're not ready in the Champions League like the other teams. Chelsea tried for 10 years to win the Champions League.
"They were probably the best team in Europe for 10 years and they won it after 10 years, probably when they didn't deserve to. They deserved to win it three or four years before."