The 17-year-old, who became the club's youngest senior debutant in 105 years when he lined up against Barnsley last season, was carried off during the 4-2 extra-time victory over Doncaster.
Manager Tony Mowbray told the club's official website: "The initial diagnosis from the hospital was there is no break but our medical staff want to do further investigations and he may have damaged ankle ligaments."
Williams was an unused substitute for the last two first-team fixtures, a 1-1 npower Championship draw with Norwich and last Saturday's 2-1 FA Cup third-round defeat at Burton.
Source: PA
