Mason rushed five times for 17 yards and failed to bring in his only target in Sunday's 34-7 preseason loss against the Raiders.
Mason struggled to find running lanes mainly due to poor offensive line play, as none of the three San Francisco backs active Sunday sniffed a 4.0 YPC average. It is worth noting that the undrafted standout from last season didn't get a carry until the 49ers' fifth drive, with Tyrion Davis-Price (9-29-0) starting ahead of him sans Christian McCaffrey (rest) and Elijah Mitchell (hip). With neither back performing well, Mason's spot on the roster is likely still secure. Perhaps the lineup swap will motivate the 24-year-old to shake off the rust against the Broncos on Saturday.