TEMPE, Ariz. -- It was late in training camp. Andre Ellington was having his usual injury troubles. Rookie David Johnson was sidelined with a sore hamstring.

The Arizona Cardinals needed to add a running back, and they found Chris Johnson, whose style fit coach Bruce Arians' system so well. On Aug. 17, Johnson signed a one-year contract with Arizona.

"He just fell into our lap," Larry Fitzgerald said.

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Johnson, a three-time Pro Bowl selection in his first three NFL seasons at Tennessee, was released by the New York Jets after one season last year. Then early on a Sunday morning, March 7, in Orlando, Florida, Johnson was wounded when someone opened fire on the van in which he was riding. A friend was killed. Johnson still has a bullet in his shoulder.

Prospective NFL employers stayed away.

"There were a lot of things going on with me. A lot of teams thought I had character issues," he said, "just a lot of stuff going on around me as far as the shooting. Stuff like that, I'm pretty sure it scared a lot of teams off. Now when I look at it, I think everything happened for a reason and that helped me land here."

There have been no apparent character problems since Johnson arrived.

Fitzgerald called him "a great teammate."

With Ellington out, Johnson moved into the primary ball carrier role. In Arizona's 47-7 rout of San Francisco on Sunday, Johnson carried it 22 times for 110 yards and two touchdowns. He also had a 40-yard reception, a play that featured one of his trademark "cut-on-a-dime" moves on the sideline. It also left him exhausted.

He is not yet in football shape.

"I was pretty tired after that," Johnson said. "Larry caught a touchdown pass right after that. It felt pretty good, but that's another reason I need to get all the way in shape because if I had to stay in and run it (on the next play), I need to be in shape to do those things."

Ellington could be back Sunday against St. Louis but coach Bruce Arians has made it clear Johnson will still have a significant role. The Cardinals' vastly improved running game is a big reason for the team's overall success, especially in the red zone, where they have scored touchdowns in 11 of 12 tries.

Johnson turned 30 on Sept. 23 but rejects the idea that that's too old for today's running backs. He notes Adrian Peterson and Marshawn Lynch are older than he is.

On Sunday, Johnson will go against a familiar foe in Rams coach Jeff Fisher. Johnson had his best seasons when Fisher was at Tennessee, rushing for 2,006 yards in 2009.

Fisher sees a lot of familiar moves on display.

"Anytime C.J. gets the ball, there's a chance that he goes the distance, so I was really impressed," Fisher said. "They're utilizing him like they should, trying to get the ball to him in the passing game and run game. He's really quick through the hole. For his size, he's got power, so on the goal line, run for a touchdown."

Johnson said he's never been surrounded with this much offensive talent before.

"It's a situation where we've so many different guys we can go to," Johnson said. "Carson (Palmer), he knows how to do it all, as far as checking in and out of the right plays. He knows when to go to the right receiver and when to check it down."

He said that just before the 40-yard pass play, Palmer said to him, "make sure you get out for me on this one `cause I might need you."

Johnson is just grateful to have a good team that needs him.

"It's a situation where, when they give you the opportunity," he said, "you've got to actually step in and make plays."