Williams (undisclosed) was placed on the reserve/COVID-19 list Friday, Tim Twentyman of the Lions' official site reports.
With D'Andre Swift (shoulder) officially ruled out, the Lions may be down to Jermar Jefferson and Godwin Igwebuike in the backfield for Sunday's game in Denver. Even Jefferson hasn't been healthy this week, missing one practice with a flu bug that's been going around the locker room, though he did return Friday as a full participant.