Mason rushed three times for 10 yards and caught his lone target for 13 yards in Sunday's 35-16 win over Arizona.
Mason was elevated to No. 2 on the depth chart after Elijah Mitchell injured his knee during the practice week. The former wound up playing eight snaps on offense (15 percent) in addition to his usual role on special teams. Christian McCaffrey ran for over 100 yards and scored four of the 49ers' five touchdowns Sunday, leaving little work for Mason despite his elevated role Week 4. The severity of Mitchell's knee injury is currently unknown, but Mason will fill in as the primary backup until his teammate returns to full strength.