The three players and Fernandinho have cost City more than £100million this summer.
"We've played a big part in the transfer market so far but it's not enough to just spend the money because a lot of clubs do that," said City captain Vincent Kompany.
"It will take something special. Buying new players is one thing but the way we have prepared is really good so far.
"There was a bit of a gap between us and the champions last season and we are doing everything to bridge that gap.
"They are important players for us this season. We needed strengthening and we have done that. We are a team that can look forward and say that we can compete on every front."