The way you look at it is this
If Kompany doesn't play are we fucked? Not really, definatley understrengthed but Kolo and Lescott can cope fine.
If Silva doesn't play are we fucked? Definatley, there is no one in the team who makes us play like he does or who creates like he does.
If de Jong doesn't play are we fucked? Definatley, there is no one in the team who can do what he does in protecting the back four.
If Tevez doesn't play are we fucked? weakend for sure but he is a goalscorer and Dzeko and Balotelli can score as much as him.
So on that conclusion de Jong and Silva are our most important players IMO. Balotelli next year will be the most important player.