Mitchell is dealing with knee irritation in addition to a concussion, and he won't practice Wednesday, David Lombardi of The Athletic reports.
Matt Maiocco of NBC Sports Bay Area reports that an MRI came back clean, but it's still unclear if the knee issue alone would've been enough to hold Mitchell out of practice had he not entered concussion protocol just two days earlier. Either way, his absence Wednesday comes as no surprise, nor does the conclusion that he's in at least some danger of missing Sunday's game against the Bengals. The good news for San Francisco is that Jeff Wilson (knee) managed a limited practice Wednesday, joining JaMycal Hasty to give the team two tailbacks (plus FB Kyle Juszczyk) at practice.