Inconsistency of MDZ is an issue. Defensively, he's off 1/3 nights. Offensively, he's been lacking this season. I would keep him 1 more year. His play making in the offensive zone CAN make a difference. Last year saw a lot of that. His ~10 goals, PP creativity, assists (primary, secondary and otherwise), he's also the only one willing to carry the puck down low and make plays. The suffering MDZ this season affects the PP and the suffering PP (Richards?) affects MDZ. Like Torts said, MDZ improves and regresses with his offensive confidence.
I think overall, it's unfair to judge our D core intuitively and without consideration for the type of zone play we're guilty of. Some players handle collapse well with shot blocking, stick positioning, IQ hockey reads, body positioning, strength and out battling opponents, intercepting pucks, clearing pucks AND board play (which we seem to think is the only way to clear the zone) etc.
It's fair to say DZ isn't above average at these skills. McD is a 9/10, G is a 8/10, DZ is a 6/10 on most nights. His board play scared me and he's out sized and matched in so many important "clear/outlet or get hemmed in for 40 secs" situations.
It's fair to say that this system and everything we know about it from offensive structure or a lack of to the way we choose to defend, does not work for MDZ. It highlights his weaknesses, neglects his strength and to top it off, our PP doesn't work at all and that doesn't help DZ's game. (I like Moore but Moore didn't fix it either, no one did, no one sucked, everyone and everything sucked).
It's difficult because this system isn't changing. His value will go down unless we might some balance in the way we play O and D.
He does need to step it up. I have no doubt in my Cresty head that he slacked off during the off season. Knowing his personality and the openness of his lifestyle, the conditioning, focus and sharpness declined as the lock out went on.
He's been the center piece to an element of our D that we desperately need to address. He has potential and he isn't that bad as a 4D as far as defense and minutes are concerned. I would give him another year AT LEAST. His value is not going to decline. GMs know and see things. Glen doesn't sell cheap, certainly not the guy that he's kept through all the trades. His skill set is going to get buyers.