Williams left Thursday's game, a 17-3 loss to the St. Louis Rams, after a fourth-quarter hit on his left shoulder.
Williams' start against St. Louis was his second of his career, and it means the running back out of Virginia Tech will have played just five games in his first two NFL seasons. He missed his entire rookie year with a knee injury. Williams had 58 attempts for 164 rush yards for an Arizona offense that is 31st in the NFL on the ground and averaging 64 rush yards per game.
The Cardinals and head coach Ken Whisenhunt now face an even more concerning situation in their backfield. Williams had taken over the starting job for Beanie Wells in the Cardinals' fourth game of the year. Wells is on the injured reserve with a turf toe injury and won't be eligible to return until at least the Arizona's Nov. 25 game against the Rams.
That means Arizona will likely go with mid-season signee William Powell and change-up back LaRod Stephens-Howling, who has also been banged up this season. Powell replaced Williams down the stretch against the Rams and has three carries for nine yards this season.
Another option for Arizona is Alfonso Smith, who signed with the team after it placed Wells on the injured reserve.