Williams (foot) is listed as questionable for Sunday's clash with the 49ers, Geoff Hobson of the Bengals' official site reports.
Williams was limited in practice each day this week. If the 21-year-old is able to suit up for Sunday's game, he would likely only provide depth for the backfield, which may be necessary for Cincinnati if Joe Mixon (ankle) -- who's also considered questionable for Sunday -- ends up sitting out.