Witherspoon was placed in the concussion protocol Wednesday, Matt Maiocco of NBC Sports Bay Area reports.
Witherspoon will need to pass through all five steps of the league-mandated protocol over the next few days to have a shot at suiting up Sunday against the Rams. If the second-year pro is sidelined for any length of time, Greg Mabin, Jimmie Ward (hamstring) and K'Waun Williams (shoulder) could all be in store for more reps in the secondary.