The weakest position group for the Steelers last year was off-ball linebacker. In the Steelers' defensive scheme, that's the inside linebacker position.
If you ask me (which I guess you did when you subscribed to this wonderful website), it wasn’t even particularly close.
The trio of Myles Jack (692), Devin Bush (659) and Robert Spillane (588) combined to play 1,939 defensive snaps last year. At a position where you should get the most "splash plays," these three combined to force zero fumbles, had zero fumble recoveries, zero interceptions and one sack.