The Manchester City stopper has enjoyed a swift rise to the top since leaving Shrewsbury for Eastlands in 2006. Hart is the number one for England and also replaced Shay Given in the City side at the start of the season.
However, his recent performances against Leicester and Aston Villa, where he played a part in Darren Bent's winning goal, have seen the 23-year-old attract some criticism.
City boss Mancini, though, has no doubts about Hart's potential and expects him to go from strength to strength, provided he maintains his focus.
He told the club`s official website: "Every player has difficult moments in their career and what he has to do is be strong at this time because when everything is going okay, it is easy for him. For a young goalkeeper to receive this criticism is a challenge and he must be strong in the face of it.
"He is always very assured, but it is important to have concentration always. He is improving but I think that he has a chance to improve more because he is young and this is his second year in the first team. He can become one of the best goalkeepers in England and the world, but for this to happen he has to want to work and want to improve."