As far as the OL goes (and most other position groups) injuries seem to drive a lot of the uncertainty. There is a stat called Adjusted Games Lost (AGL) that documents how many game days were lost by a team due to injury. This stats has been pioneered by Football Outsiders.
To put it in even greater perspective, if you look at the teams that are in the top 10 as far as AGL goes (the 10 teams with the fewest # games lost to injury), you have in that list most of the teams that went deep in the playoffs.
So I think that we need to get a handle on the injuries. If we do, Kush and Long will contribute all season long and the OL will be solid.
I think that's the key to success. Unfortunately the lock to that success isn't a pin tumbler, it's an EVVA MCS lock. It involves personnel selection (who we choose in the draft and FA) and their history with injury and with strength training and conditioning, practice structure, nutrition, off-season work, in house strength and conditioning and genetic responses to all those factors. The positive to me is that, Whitehair, Leno and Massie all seem to be durable players who've fit well into the systems theBears have used with them. That's a strong base. It's one I think the team needs especially with the depth at the interior of the line as opposed to the exterior.