There is basically one season in Mike Tomlin’s history in which he took a running back by committee approach, and even that was influenced by injury. At the end of the 2011 season, Rashard Mendenhall tore his ACL, and was not ready to return at the start of the next season. Jonathan Dwyer and Isaac Redman split the bulk of the touches.
The next year, they drafted Le’Veon Bell. And James Conner has largely slid into that workhorse back role over the course of the past two seasons as well, while he has been healthy. Though the running backs in the offseason last year talked about having more of a rotation, it didn’t really develop while Conner was available.