Mitchell (shoulder) wasn't present at the start of Thursday's practice, Matt Barrows of The Athletic reports.
After getting banged up Week 2 at Philadelphia, Mitchell was diagnosed with what coach Kyle Shanahan called a shoulder injury that's "a little worse than a stinger," per David Lombardi of The Athletic. There's still a chance Mitchell gets cleared to play Sunday night against the Packers, as does Trey Sermon, who is in the concussion protocol but was limited Wednesday. Elsewhere in the backfield, Raheem Mostert had season-ending knee surgery after Week 1, and JaMycal Hasty is slated to miss multiple games with a high-ankle sprain, leaving Trenton Cannon and Jacques Patrick as the only healthy RBs on the active roster. Meanwhile, Kerryon Johnson and Chris Thompson are stashed on the 49ers' practice squad as potential elevations.