For as long as Mike Tomlin has been around, the Pittsburgh Steelers have not been a team that has bought into the trend of specializing at the running back position. They have not had a designated goal line or short-yardage runner, nor ever much of a third-down back, with perhaps the exception of Mewelde Moore early in his tenure due to injury. Anything else has been a short-lived experiment at best.
Every back on the roster is at some point going to be asked to do everything. That has been true of almost everybody, shy of Dri Archer, and maybe Chris Rainey as well.