To my mind, there are three basic tiers of coordinators (or head coaches who basically act as one unit's main coordinator).
Top: These guys consistently get more out of their talent than just the sum of the parts. Current examples include Vic Fangio, Bill Belichick, Ron Rivera, Wink Martindale, Mike Zimmer.
Middle: These guys basically give you back what you put into the defense. If you invest a lot, they can coach up a great unit. If your personnel is poor, so will they be. Most of the league's coordinators reside here. Current examples include Mike Pettine, John Pagano, Gus Bradley, Jack Del Rio, etc, etc.
Bottom: The other end of the bell curve, these guys somehow manage to give you back less than the sum of the talent they're given. In recent seasons, I would put guys like Matt Patricia, Paul Guenther, and Mike Nolan in this tier.
Most of the veteran coordinators out there seem to belong to the middle tier OR they're really old, to the point that it's unclear what they really have left.
Chances are that any young guy hired will fall into that middle tier as well, but those guys also have the potential of being top tier guys.
Given that this should be a coveted job, and allowing that the Packers vet candidates properly, I am not too concerned about them ending up with a guy from the bottom of the barrel.