Mason is expected to take over as the 49ers' lead back after Christian McCaffrey (Achilles/calf) was placed on injured reserve Saturday, Nick Wagoner of ESPN.com reports.
With Elijah Mitchell out for the season and McCaffrey out until at least Week 6, the San Francisco backfield looks like it'll belong to Mason, who carried 28 times for 147 yards and a touchdown while adding a five-yard reception in the 49ers' Week 1 win over the Jets. Receiver Deebo Samuel (eight carries in Week 1) is also likely to see more involvement on the ground in McCaffrey's absence, while rookie Isaac Guerendo could also become more of a factor in a change-of-pace role once he's further removed from the hamstring and groin injuries that cost him considerable time during training camp and the preseason. Mason has probably already been rostered in most competitive leagues, but managers in shallower leagues should take a peak at the waiver wire in case he's still available.