Richards has been in fine form for the Barclays Premier League leaders this season but has not been able to force his way back into national team boss Capello's thinking. The 23-year-old won the last of 12 caps against France a year ago and was overlooked in favour of Glen Johnson and Kyle Walker for the recent friendlies against Spain and Sweden.
Mancini said: "Micah is young. I think in the last year he has improved a lot as a player but I think he needs to improve more because he has good quality. Sometimes Micah is too strong - he thinks he can play at 50%. But if Micah played 100%, for me, he becomes one of the top full-backs in Europe."
Richards, who was first capped by England in November 2006, is an impressive attacking force but has sometimes been criticised for his defensive abilities and positional sense.
Mancini accepts there are faults, but believes Richards has improved considerably since his last conversation with countryman Capello about the player earlier this year and expects him to get even better.
Mancini said: "His body is on the pitch but his mind is at home, sometimes! This he can improve. He should remember to pick up his brain!
"But I say this because I love Micah as a guy, as a player.
"I don't think he can lose time because he has everything - he is strong, quick, strong in the air, he can play in a different position.
"We (Capello and Mancini) spoke about Micah about six months ago. It is my opinion that Micah has improved a lot in the last year but he can improve more.
"For Capello, I don't think it is easy to choose between a lot of good players. It is clear that some should stay at home for the European Championship but I hope Micah can get into the national team."
Source: PA
Source: PA