Middleton is a run of the mill bottom pair defenseman. Maybe I'm off base here on what those guys tend to earn, but 4x4 is a lot for what he is. It's probably not a lot for the role he's been playing, but that's the same issue that led to Foligno getting 4x4 too, guys getting paid for a role they filled rather than what they are.
That said, I wouldn't have as much of an issue with Middleton getting the 4x4 as I do with Foligno because Middleton is still relatively young without the injury history Foligno has, and he does seem to click well with both Spurgeon and Faber. But still, LD is one of the spots we need to upgrade if we want to be a real team, and that would result in Middleton being pushed down to the bottom pair.