Well, he does kind of defend against the pass and the run simultaneously better than Wilson and Scott. Is he a Polamalu clone on that matter? Far from it, but I have this hunch, that the coaching staff would rather not mess with the continuity in the defensive backfield and keep Scott and Wilson as situatinal players.
If you have to overpay a little, I would think about it and maybe reach Whitner's demand. Knowing what Whitner wants is key.