Mostert carried the ball five times for 11 yards but lost a costly fumble in Sunday's 28-18 loss to the Cardinals.
Mostert received a season-high five carries after Matt Breida (ankle) was knocked out of the contest. The special teams ace failed to capitalize on the opportunity, losing an untimely fumble as the 49ers attempted to make a comeback in the second half. Breida's status for next week's matchup is up in the air, but the more likely scenario is additional volume for Morris -- rather than a timeshare with Mostert -- if Breida is unable to go.