TEMPE, Ariz. -- The Arizona Cardinals' already embattled ground game has taken a severe blow with the announcement that running back Ryan Williams is out for the season with a left shoulder injury that will require surgery.
The Cardinals already are without Beanie Wells until at least Thanksgiving weekend because of a severe turf toe injury.
The hard-luck Williams missed all of his rookie season a year ago with a torn patella tendon. He injured his shoulder on a hard hit during last Thursday night's loss at St. Louis.
The Cardinals are 4-1 despite their virtual lack of any ground game. They rank 31st out of 32 NFL teams in yards rushing per game at 63.4. Only Oakland's 60.8 is worse.
Coach Ken Whisenhunt revealed the extent of the injury in his brief meeting with reporters following the team's light workout on Monday.
"The timetable for recovery is probably three months, so that puts him out for the season," Whisenhunt said.
Asked if the team would look to bring in a running back from elsewhere, he said, "We'll look and see."
"I feel good about the guys that we've got," the coach said. "We're always going to look to get better at every position. If that opportunity is there, then we'll certainly try to act on it."
The Cardinals didn't immediately add a running back when they placed Williams on injured reserve Tuesday, instead adding cornerback Crezdon Butler, who spent the preseason with Arizona until he was released in the team's final roster cuts on Aug. 31.
Arizona opened the season believing that its ground game would be a strength with Wells and Williams providing a solid 1-2 punch. Now that punch is down to 0-0.
"That's the NFL," Whisenhunt said. "Teams have to fight through adversity and keep going. We've done a good job of that the first five weeks of the season, and now we've got another challenge, but that's OK. We'll work through it."
Wells was off to a slow start as he recovered from knee surgery, then went down with the toe injury in week 3 against Philadelphia. The Cardinals placed him on the NFL's new injured reserve/designated for return list. That rule requires Wells to miss the next five games. He can return for Arizona's home game against St. Louis on Nov. 25.
Williams, a second-round draft pick from Virginia Tech in 2011, moved into the No. 1 running back spot and had a strong second half against the Eagles. But he and any other running back who carried the ball has had a tough time in the two games since then as the Cardinals managed 28 yards rushing in an overtime victory over Miami, followed by 45 in Thursday night's 17-3 loss to the Rams.
Williams, who didn't take an NFL snap last season, had gained 164 yards in 56 attempts, an average of just 2.8 yards per carry. He has caught seven passes for 44 yards.
"I feel horrible for Ryan," Whisenhunt said, "but what I told Ryan when we sat down was that at least he won't have to deal with it through an offseason. He'll be able to go through the offseason program. He'll be able to go through practices and that will get him in better shape and ready to go next year."
The injury is more bad news for quarterback Kevin Kolb. The lack of a running threat had been a major contributor to the intense pressure from the pass rush faced by Kolb and his team's struggling offensive line. Kolb has been sacked 17 times in the last two games, eight by Miami and nine by St. Louis.
Information from The Associated Press was used in this report.