The 20-year-old Serb has made a big impression since joining the club from Fiorentina last summer.
He arrived expecting to have to wait for an opportunity but manager Roberto Mancini thrust him into the heat of a Champions League match at Real Madrid and was immediately vindicated.
Nastasic soon broke up the established title-winning centre-back partnership of Vincent Kompany and Joleon Lescott and has now started 30 games in all competitions.
Having been rested for the midweek Premier League win over West Brom, Nastasic now looks likely to start at Wembley in the FA Cup final against Wigan.
Nastasic said: "To be honest, it has been perfect for me.
"Obviously, I was expecting at least six months to create (a chance in the team) and be feeling the moment, but I am happy that I have already arrived at this level."
Nastasic has shown little sign of being overawed since his debut at the Bernabeu and feels he belongs at the top level.
He said: "To be honest it was an important game but it is more important now we play against all the big teams. We know this is a very big game and is very important for us and I am only looking forward.
"I know how important it is for the supporters and everyone at the club. We are all ready for it."