Cardinals running back Kerwynn Williams carries the ball against the Titans.

There is a possibility Adrian Peterson's bothersome neck injury could keep him out the rest of the season.

The veteran running back didn't practice Wednesday after missing the past two games, and coach Bruce Arians said he has "no idea" if Peterson will play again in 2017.

If he cannot, the Cardinals will continue to roll with their fourth starting running back. So far, that hasn't been an issue.

Kerwynn Williams has made a career out of being an extremely useful Band-Aid, and the theme has continued the past two games. He has carried the ball 36 times for 170 yards against the Rams and Titans despite playing with several cracked ribs.

"The way he's been running the football lately – getting through the initial line of defenders, getting into the linebacker corps, making some moves, getting into the secondary – it's really keeping our offense ahead of the chains," quarterback Blaine Gabbert said.

Williams doesn't have ideal physical attributes like Peterson or running back David Johnson, but his production has regularly outpaced expectations. Williams, a former seventh-round pick who has been cut and re-signed multiple times by the Cardinals the past few years, said it's his work ethic that has helped him carve out an NFL niche.

"I've never been anyone's first pick, ever," Williams said. "I've never relied on somebody else picking me. I've always picked myself first. I really try to outwork the doubt."

Williams has always been a talented runner, but early in his tenure with his team, he didn't contribute in the passing game or on special teams. But through hard work, he improved.

"He couldn't catch punts two years ago to save his life, but he catches them real good now," Arians said. "That's just Kerwynn. Whatever it takes for him to make the team, he's going to do it. Then when he makes it and you put him out there, you're getting his best."

Williams has made it to his fifth NFL season and is averaging 4.8 yards per carry for his career. He's happy with the way things have turned out, but won't ever rest on his laurels.

"When you have to work for things in life, I think it does make you appreciate things a lot more," Williams said. "You realize all that you put in to get to that point, and you don't want to do anything to lose it. So you work that much harder to keep yourself in that position."

KHALIF BARNES HAPPY TO CONTINUE CAREER

There are only three weeks remaining in the season, so it would have been understandable if 35-year-old Khalif Barnes declined a tryout with the Cardinals on Monday. The veteran offensive tackle was mulling retirement already, and was busy home-schooling his kids in Houston.

But Barnes chose to work out for the team and showed enough to get signed in the wake of Jared Veldheer's season-ending ankle injury.

"I was coming to the realization it might be the end," Barnes said. "After today, and after the call Monday, I really don't think I want to go until someone tells me I can't come back anymore. The older guys who tell you, 'Play until they kick you out' – I felt that today."

Will Holden is projected to start at left tackle in place of Veldheer on Sunday, and Evan Boehm will fill in for Earl Watford (ankle) at right guard. Barnes is only an emergency option, but he's on a team again after sitting unemployed for several months – the first time that's happened to him in his 11-year NFL career.

"I would've liked to be here a couple of weeks before, but I am blessed and lucky to be here," Barnes said. "It's a dream come true."

BAKER, BETHEA MISS PRACTICE

Safeties Budda Baker (thigh) and Antoine Bethea (knee) missed practice on Wednesday, but Arians expects them both to return on Thursday. Defensive lineman Josh Mauro (ankle) and linebacker Gabe Martin (hamstring) also didn't practice due to injury, while linebacker Karlos Dansby, wide receiver Larry Fitzgerald and defensive lineman Frostee Rucker were given days off.

Guard Alex Boone (back), wide receiver John Brown (toe), linebacker Chandler Jones (hip) and defensive lineman Corey Peters (ankle) were limited.

For Washington, cornerback Josh Norman (knee), linebacker Zach Brown (illness/toe/Achilles/hip), tackle Trent Williams (knee), safety Montae Nicholson (concussion) and tackle Morgan Moses (ankle) didn't practice. Those limited were linebacker Ryan Anderson (ankle), wideout Ryan Grant (ankle), wideout Maurice Harris (concussion), defensive lineman Terrell McClain (toe) and center Chase Roullier (hand).