Williams' absence Thursday was the result of a hip injury and an illness, Tim Twentyman of the Lions' official site reports.
Williams appeared on the Lions' initial Week 6 injury report as a limited participant at Wednesday's practice, with only the hip issue attached to his name. His downgrade to no activity a day later with a new health concern in tow likely points to the illness being at the root of his absence, rather than any sort of setback with his hip. So long as he can get back on the field in some capacity Friday, Williams would still be in good position to complement D'Andre Swift (groin) out of the backfield during Sunday's game against the Bengals.