League sources told ESPN, the Chicago Sun-Times and the Chicago Tribune that Williams was put on the list after testing positive for COVID-19. If the tailback is asymptomatic and vaccinated, he would be allowed to return once he produces two negative test results at least 24 hours apart.
If Williams is vaccinated but shows symptoms, he would be able to return once he has two negative tests 24 hours apart and is asymptomatic for 48 hours. If he is unvaccinated, he will have to quarantine for a minimum of 10 days.
The timing of Williams' placement on the COVID-19 list provides another problem for the Bears' backfield. Chicago is already without top running back David Montgomery, who is on injured reserve because of a knee injury.
If Williams is forced to miss Sunday's matchup against the Packers, rookie tailback Khalil Herbert would have a large role for the Bears. Herbert -- a sixth-round draft pick in this year's NFL Draft -- had 18 carries for 75 yards in last week's 20-9 win over the Las Vegas Raiders.
The Bears also have veteran tailback Ryan Nall on the active roster and Artavis Pierce on the practice squad.