Mitchell sustained a shoulder injury during Sunday's game in Philadelphia, Nick Wagoner of ESPN.com reports.
Mitchell didn't join his teammates for the 49ers' third possession of the second half, instead getting his shoulder looked at by the training staff, per Matt Barrows of The Athletic. If Mitchell is unable to return, he'll finish Week 2 with 14 carries for 32 yards and two catches (on two targets) for 11 yards. JaMycal Hasty took over the primary RB role in Mitchell's absence.