Hart has enjoyed a swift rise to the top since leaving Shrewsbury for Manchester City 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.
"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," he told the club's official website.
"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."
England boss Fabio Capello also weighed into the debate earlier this week, telling Hart he must be switched on for every game.
"He has made mistakes but he is young," Capello said. "It is important for England that he is able to remain focused in every moment of the game.
"It is difficult to play in a team that spends a lot of money and needs to win. You have to understand that when you play against other teams who are in the middle of the table or lower, this team will play against you and give 110% to beat you.
"For this reason he has to play every time at the top because he has to be focused only on the game."