Smallwood was placed on injured reserve Monday with a knee injury. Marshall, a former Oregon standout, spent the offseason and preseason with the Eagles and has been on practice squad all year.
Darren Sproles is in the league-mandated concussion protocol, leaving the Eagles even thinner at running back. Ryan Mathews and Kenjon Barner are the top only other running backs on the roster, so Marshall could play Sunday against the Baltimore Ravens if Sproles has not recovered from the concussion.
Mathews figures to get the bulk of the work but the Eagles have used as many as four RBs in games this year. Marshall likely won't get enough work to warrant a start in just about any format.