The Seattle Seahawks are releasing running back Chris Carson with a failed physical designation, a source confirmed to ESPN.

Carson is leaving the door open to play in the NFL again, but he's been trying to rehab a neck injury that ended his 2021 season and it hasn't fully recovered, the source said.

Carson's departure is a blow to Seattle's backfield but not a surprising outcome given the uncertainty as to whether he'd return from a career-threatening neck injury. Multiple Seahawks sources have expressed doubt in recent months that he'd be medically cleared after having what coach Pete Carroll described as fusion surgery in December.

The team has been preparing to proceed without him, re-signing Rashaad Penny in March before drafting Kenneth Walker III in the second round of April's draft.

NFL Network first reported Seattle's plans to release Carson.

Carson appeared in the first four games of last season and was unable to return because of his neck injury. Carroll said last month that Carson still didn't have full range of motion and had yet to be medically cleared. He said Carson was "concerned" about his playing future.

Carson, 27, rose from a seventh-round pick out of Oklahoma State in 2017 to one of the league's most physical runners when healthy. He began all five of his NFL seasons as Seattle's starter, beating out free agent signing Eddie Lacy as a rookie and then Penny, Seattle's first-round pick the following year. He topped 1,100 yards in 2018 (14 games) and 2019 (15 games), the two healthiest seasons of what has otherwise been an injury-marred career. In doing so, he became the Seahawks' first back since Marshawn Lynch in 2013-14 to post consecutive seasons with at least 1,000 rushing yards.

For his career, Carson has rushed for 3,502 yards and 24 touchdowns on 769 attempts (4.6-yard average) in 49 games. Spotrac.com lists him with $9.5 million in gross on-field earnings to this point.

Penny, who led the NFL in rushing over the final five weeks of last season, is in line to be Seattle's primary running back after returning on a one-year, $5.75 million contract. He's missed 30 of a possible 69 career games (including playoffs) due to injury. That, combined with Carson's uncertain future, was why the Seahawks reinforced their backfield by drafting Walker 41st overall.

ESPN's Jeremy Fowler contributed to this report.