He hasn't been the same since he suffered an injury earlier in the season. I think he rushed himself back after seeing the impact Ridley was making thanks to his absence, and I think he forced himself back onto the field before he was really ready. He clearly isn't quite as quick as he was before he got hurt, and I think they used him on kickoffs primarily to limit his play until he's fully healthy, much like they did with BJGE and the same reason they held out Ridley.
But I agree with the playcalling regarding the lack of screens. That's an area that the line has been great at, blocking downfield, etc., and I'm surprised with the amount of bliztzing they did (Brady said after the game the Steelers blitzed on more than 50% of the plays) we haven't seen more of that.
