Alfonso Smith is a candidate to replace Ryan Williams in a running back role after Williams' season-ending knee injury suffered Friday night.

In a quiet and nearly empty locker room late Friday night, Alfonso Smith returned from his own stint in the training room to get dressed for the long plane flight home from Green Bay, realizing his professional life had just changed.

Smith, who was back and forth on the Cards' practice squad and roster last season, suddenly went from possibly cut to possibly playing a big role for the team in 2011 once rookie Ryan Williams was carted off with a knee injury during the game.

"I feel like I don't have a choice," Smith, a 6-foot-1, 208-pound speedster from Kentucky. "I have to be there for my teammates. I've got to step up and make plays. I will be ready whenever they call my number."

Coach Ken Whisenhunt delivered the expected news Saturday afternoon, that Williams indeed had a ruptured right patellar tendon and that his season was over. Williams is expected to have surgery early this week, start rehabilitation as soon as possible, and Whisenhunt said the hope is to have him back by training camp next year.

Whisenhunt called Smith a "viable candidate" to move into the running back mix. Beanie Wells will be the starter, and Whisenhunt said Wells had more on his shoulders this season regardless of whether Williams would have remained healthy. LaRod Stephens-Howling will also get some time, but at his size, he can't fill Williams' role.

The Cardinals will have to add a back, he said, but to what degree that new player will be – whether it's just a camp body to take some practice reps or a legitimate candidate to play – is yet to be determined.

Whisenhunt also said that could be an ongoing process, meaning the Cards could sign someone now and make another move later when teams make their roster cuts heading into the regular season.

"It has to be the right fit," Whisenhunt said. "We have a pretty good chemistry with our team and that group."

Whisenhunt referenced a moment in the 2010 preseason finale, when Smith had to decide to either go out for a screen or move downfield depending on a blitz that may come. Smith read it right, made the catch and a big gain, which helped cement the win.

Smith works hard in practice and has speed, Whisenhunt said, "but I have been most impressed with the work he has put in to understand our offense."

Smith had 33 yards and a touchdown on 12 carries against the Packers. Smith also can play special teams.

"My feeling is just to take advantage of every opportunity I am given," Smith said. "If it weren't for the Man upstairs, I wouldn't have the opportunity. I wouldn't have done what I did out there (in Green  Bay)."

Finding a back isn't always as hard as other positions. The Packers lost starter Ryan Grant early last season with a bad knee injury and eventually rode lightly regarded James Starks, a one-time sixth-round pick, to a title. The Saints used undrafted Chris Ivory more effectively than Pierre Thomas or Reggie Bush.

Whisenhunt said there was no regret in trading veteran back Tim Hightower to Washington, not that it's a surprise. With Williams' emergence and Wells' improvement, there wouldn't have been the touches or the playing time for Hightower.

"The easy thing is always to second-guess," Whisenhunt said. "It can happen at any position.
"(The trade) was the best situation for both parties, for us and for Tim, and that was something we had to consider."

Whisenhunt expressed optimism Williams will come back. Former Buccaneers running back Cadillac Williams had his career derailed by the injury, but he ruptured the patellar tendon in both knees in consecutive years.

Hall of Famer Jerry Rice and former Falcons cornerback Juran Bolden are among the players who came back from patellar injuries and played for many more years.

"There are many success stories," Whisenhunt said.

Ryan Williams' success story was supposed to be what he did on the field as a rookie. But his mood is upbeat and he has let loose many statements on his Twitter account promising a full recovery and impressive return.

That's a long way off, however.

"(Ryan) and LaRod and Alfonso and Beanie, they all have different styles," quarterback Kevin Kolb said. "They all bring something to the team. Ryan had his certain style. We had seen it, it was shifty. He was getting better at protections. There were high hopes for him, and there still are high hopes for him. Obviously this is a setback."