I think he will be back, and will be fine. Coming back after al that time off of football, his body wasn't ready possibly. I think his mindset is.
Give him an off season to get his body in better shape. As for the head injuries in 2 consecutive games, that happens often it seems.
Lee, is another story, but as I said in another pot, it took Murray to this point and stayed healthy, other than the broken hand, but played all 18 games. May 2015 will be Lee's year too.
With the emergence of Hitchens, and if Durant returns, and I wouldn't be opposed to bring Carter back. Their are 2 guys for depth right there.
C. Lawrence and even Wilber can be replaced in the draft or via FA. But I would be ok with Wilber too.