The 49ers will place rookie running back Joe Williams on injured reserve, according to Tom Pelissero of NFL Media.
The fourth-round pick injured his ankle in the preseason finale Thursday night when he played 26 snaps against the Chargers. He rushed for 53 yards on 10 carries, caught two passes for 2 yards and lost a fumble.
In four exhibition games, Williams ran for 130 yards on 20 carries, as undrafted rookie Matt Breida passed him on the depth chart.
Reserve running back Raheem Mostert has made the team, at least for now, according to a tweet from his agent. But the 49ers likely keep an eye on running backs released today for depth behind Carlos Hyde, having released Tim Hightower and Kapri Bibbs on Friday.