The Rams placed Williams (ankle) on their injured reserve list Tuesday.
Williams suffered a high-ankle sprain Thursday versus Buffalo and is expected to miss 6-to-8 weeks, Sarah Barshop of ESPN.com reports. The move to the injured reserve list means he'll certainly miss at least the next four games. In his absence, Jake Funk could be in line for a few spare snaps at running back, and Brandon Powell will continue to operate as the Rams' primary kick returner.