Former All-Pro running back Adrian Peterson has been out for the Arizona Cardinals for several weeks due to a lingering neck injury, and it now appears that he won't return this season.

Head coach Bruce Arians voiced concern for Peterson's health on Wednesday, saying he has “no idea” when the 32-year-old will make his return, according to Adam Schefter of ESPN.

The Cardinals haven't indicated precisely how Peterson suffered the injury, and he hasn't shown any significant progress in his recovery since going down during the Cardinals' 27-24 win over the Jacksonville Jaguars on November 26th. In six games with Arizona, he has 448 rushing yards on 129 carries with a pair of touchdowns.

Peterson's production has fluctuated greatly in his brief time with Arizona. He's posted a pair of performances with more than 130 rushing yards, but he has also failed to crack 30 yards on the ground on three occasions.

In his absence, backup Kerwynn Williams has held down the starting spot, racking up 170 rushing yards on 36 carries over the last two games.

If Peterson is unable to suit up against the Washington Redskins on Sunday, Williams will likely continue to hold down the primary duties in the running game.