Mitchell (concussion/knee) has been ruled out for Sunday's game against Cincinnati, Matt Maiocco of NBC Sports Bay Area reports.
With the knee injury not considered serious, it would seem Mitchell hasn't made enough progress in the concussion protocol to practice or play. His upcoming absence leaves Jeff Wilson and JaMycal Hasty to man the San Francisco backfield Week 14, with Trey Sermon (ankle) still on IR and Trenton Cannon (concussion) ruled out for Sunday.