By FOX SPORTS Staff
Nastasic joined City during the summer and has thus far made 17 Premier League appearances for the club, 10 of which resulted in clean sheets for the Citizens, the latest being their 1-0 win over Aston Villa on Monday.
The Serbian centre-back's no-nonsense tackling and excellent reading of the game has made him a firm favourite with the City faithful, and his superb performances at the back have better helped the team cope with the absence of captain Vincent Kompany, who has been struggling with a litany of injuries this season.
Mancini admits that he too has been impressed by Nastasic's recent displays, but the Italian tactician claims the 19-year-old can get even better.
"We don't have Vinnie [Kompany] at the moment and he's very important to us but Matija [Nastasic] is playing very, very well at the moment," Mancini was quoted as saying by the official City website.
"He's young and he probably needs to improve - he needs to learn the Premier League more but I'm very happy with his performance on Sunday and in the last game.
"Vinnie will be back for either for the FA Cup game against Barnsley or against Everton the week after.
"We had three or four games like QPR, West Ham, Chelsea where we deserved to win and missed chances to score but sometimes it's enough to win 1-0 like on Sunday and to fight for every ball."
Mancini also revealed that he was impressed with relegation-threatened Villa and tipped Paul Lambert's men to stay in the Premier League.
"Villa are a good team, they have a very young team and maybe they need some experience but they play good football," Mancini added.
"They will stay in the Premier League I think."
City's next fixture sees them take on Barnsely in the FA Cup.