Awaiting word on Cards' Ryan Williams

The Arizona Cardinals' offense took a hit Friday night when rookie running back Ryan Williams left the team's preseason game against Green Bay on a motorized cart.

Replays showed a Packers player landing on the back of Williams' lower right leg.

There was no immediate word on the severity of the injury, but replays left the impression the injury could be serious. Williams had dazzled during training camp and was expected to push Beanie Wells for the starting job eventually.

Arizona traded running back Tim Hightower to the Washington Redskins after the Cardinals used a second-round choice for Williams. Wells ran aggressively and effectively against the Packers. Injury problems have slowed him previously.

LaRod Stephens-Howling and Alfonso Smith are the only other halfbacks on the roster. Reagan Maui'a and Anthony Sherman are fullbacks.

UPDATE: The Cardinals said Williams injured his knee and would not return to the game.