Harrison is attempting to return from a torn ACL sustained last January and was not expected to be able to play, despite head coach Mike Tomlin leaving open the possibility. In fact, Harrison stated after practice on Friday that he has yet to rule himself out of the game, even though he missed the team's two most recent practices and was limited in action on Wednesday.
While he has yet to rule himself out, it's unlikely that he will play.
In order to become eligible to return, the 34-year-old will need to receive medical clearance from the Steelers' medical staff. As of earlier this week, he had yet to receive that clearance.