Mitchell (knee) was listed as a non-participant for Tuesday's walk-through practice.
The 23-year-old hasn't logged any practice activity since suffering a concussion Week 13 versus the Seahawks, but he's since cleared the NFL's five-step protocol for head coach injuries. At this stage, Mitchell is still trying to work past a knee issue, though head coach Kyle Shanahan said Tuesday that Mitchell did "some encouraging things" despite not taking part in the walk-through, according to David Lombardi of The Athletic. General manager John Lynch was similarly positive about Mitchell's situation Tuesday, noting that the running back has "taken a positive turn" in his recovery, per Cam Inman of The San Jose Mercury News. Even so, Mitchell likely will need to show more tangible signs of progress at Wednesday's session to have a legitimate chance of suiting up Thursday at Tennessee. If Mitchell ends up missing a third straight game, Jeff Wilson will get another turn as San Francisco's lead back.