I'm sure there's a combination of things that are hurting our run game, but from what I see, we simply don't have backs that are explosive. Murray is essentially a plodder at this point... he'll get you 3-4 yards up the middle and will spring bigger plays if it's blocked well, but other than that, he's just going to get what is blocked for him. I can pretty much say the same for Bell and Freeman.
Clearly Williams is in the doghouse for sucking in pass protection, but he's easily the most explosive back I've seen of the bunch this year, and he's the only guy I see who is able to bounce to the perimeter and get yardage outside.
What I'm seeing from Detroit and Denver is that they're just flooding between the hashes, because they don't think any of our backs have the speed to get outside or can run the stretch/outside runs, and they're probably right. That's where missing Dobbins hurts so much, because he had the speed to make linebackers pay on the perimeter for collapsing too quickly. And because of that, it opened up the middle for Edwards.
And honestly, I'm not sure I see a fix for this. I think it's somewhat a talent issue.