Chris Johnson is back in the mix at running back after re-signing before training camp

Training camp used to be a slow build for Andre Ellington.

The Cardinals running back would get his work in, but because he was a starter, the end goal was to peak during the regular season.

That luxury is no longer available. Injuries have sidetracked Ellington's once-promising career, and now, a ho-hum camp could mean no regular season at all with the team.

"I've got to kind of remind everyone of what I'm capable of," Ellington said. "I've got to come here with a chip on my shoulder as opposed to a couple years ago."

Ellington is one of several established running backs jockeying for position behind star David Johnson on the depth chart.

The Cardinals re-signed Chris Johnson before training camp began and return Kerwynn Williams, who impressed late in the year. Speedy T.J. Logan was drafted in the fifth round, while Elijhaa Penny is trying to turn heads after a year on the practice squad.

The Cardinals usually keep four running backs on the roster but will stretch it to five if that many impress.

"It depends on the rest of the roster right now," coach Bruce Arians said. "The fourth tight end, the sixth receiver, the fifth running back, the ninth lineman – they're all fighting. You're not going to cut a (better) player for another position. You're going to keep the best players."

Williams didn't make the team out of camp last season but was re-signed early and eventually ascended to the backup role. He finished with 18 carries for 157 yards and two touchdowns with an eye-popping 8.7 yards-per-carry average.

While Williams only has 98 carries in his career, he's averaged 5.6 yards per tote, and yet, he still must fight for a spot.

"All I do is grind," Williams said. "That's all I've ever been taught to do. That's how I grew up. That's what I'm going to continue to do. I've had to work for everything I've ever gotten, and I don't want it any other way. I value it that much more because I had to grind for everything I've got."

Chris Johnson had an impressive start in 2015 after joining the Cardinals in camp, rushing for 814 yards through 11 games, but injuries have since hindered him. Johnson, 31, seems like the favorite to resume his role as David Johnson's backup provided he stays healthy.

"He's one of those genetic guys that just never gets old," Arians said.

Logan has the young legs and has made a favorable impression during camp. He's trying to soak up everything he can from his position-mates. David Johnson is one of the league's best backs, Chris Johnson has a 2,000-yard rushing season and Ellington has been a pivotal piece in the past.

"Those guys have had a lot of success, and no matter what I do my first year, I'll never match up to that success," Logan said. "I want to compete, learn from them guys."

Ellington's roster spot seems to be most in peril among the established returners. He said a mental block from a string of injuries hurt him in the past, but he's back to welcoming contact between the tackles. It's audition time for him, and he's hoping to seize the opportunity.

"I know there are still a lot of Ellington fans out there and I want to excite them," Ellington said. "Make a play here or there. Show them I've still got a little juice in the tank."

No matter how the depth chart shakes out, the Cardinals should have enviable options in reserve.

"We have a talented group," Ellington said. "The plus side of it is, it's bringing the best out of everyone."