Linebacker coach, secondary coach, offensive line coach, and the strength and conditioning coach.
The OC may retire but if he stays they certainly need to hire a real QB coach instead of letting a grad assistant handle it.
I think the DC needs to do more, and coach the linebackers or defensive backs as that would help with the apparent disconnect with the defense.
Additionally, the tackling must improve dramatically, it has been horrible all season starting with the Appalachian State game. Unfortunately, the blocking on offense hasn't been much better than the tackling.