Mack was only on the field for three special teams snaps in Sunday's 11-10 loss to Denver.
Mack was signed from the practice squad to replace the injured Tyrion Davis-Price and serve as the team's third back. The former Colt didn't get involved in the offensive game plan, but the veteran's track record of success (1,999 combined rushing yards and 17 touchdowns in 2018 and 2019) could see him jump ahead of undrafted rookie Jordan Mason (five offensive snaps) as Jeff Wilson's backup while Davis-Price recovers from an ankle injury. Neither backup is worth rostering in fantasy so long as Wilson and Deebo Samuel dominate the backfield touches in San Francisco.