You seem to be indicating that he never showed potential to be a top-pairing guy and that people were just enamored with his big hits, and I'm just saying that's not true. This isn't a case of people going full Dion, in fact I'd argue that apart from a big hit along the boards here and there (which frankly aren't THAT spectacular) there isn't much highlight-worthy stuff from Zads.
A guy doesn't have to be productive in order to be a defensive force, he just has to be able to neutralize offense in the defensive zone and move the puck out. In those instances (again, small sample size alert) where he has been playing solid hockey he's doing just that. Before he got hurt last season he played as well as we've ever seen him.
MHH just did an article indicating that he and EJ are actually not compatible at all as defensive partners. Not only are EJ's numbers better away from Zads, but Zads' numbers away from EJ are better as well. If/when he gets back into the lineup I hope the number crunchers are doing their job in Denver and telling Bednar NOT to put them together period, and I hope Bednar listens.