I don't think he is Cabaye's replacement at all. That is more likely to be Cabella or whichever AM we are trying to get. Whether we get Cab's replacement with our transfer policy is a different story of course.
No doubt that Colback is not here as a back-up player at all though.
Logically though he is. We haven't got Cabella and I can't see us getting him. We lost Cabaye and now now pardew is talking about Colback as a starter. If you look at it that way, he's replaced a player that left. Happy days
no other way to look at it imo. Central mid, viewed as key player by manager. Until such time (guess: never) as Cabaye is replaced by a player of similar quality, Colback will effectively be his replacement.