San Francisco 49ers 'nervous' about knee injury of RB McKinnon

The 49ers reportedly fear a torn anterior cruciate ligament after McKinnon went down during a non-contact play.

San Francisco 49ers running back Jerick McKinnon suffered a potentially serious knee injury during Saturday's practice and is slated to undergo an MRI exam to determine the severity.

The 49ers reportedly fear a torn anterior cruciate ligament after McKinnon went down during a non-contact play.

"We're concerned about it, but we don't have an MRI done so we don't know for sure," San Francisco coach Kyle Shanahan told reporters. "We're nervous about it, that's for sure."

McKinnon fell awkwardly after making a cut on the play, which raised the level of concern.

"Yeah, I mean anytime I watch someone feel their knee, there's always that concern," Shanahan said. "But I have felt that way before and it hasn't been (an ACL), so I'm not trying to (make this) the darkest moment in the world right now. We hope that we're wrong."

McKinnon is just getting back into the mix after suffering a strained calf on Aug. 12. He was expected to start the Sept. 9 opener against the Minnesota Vikings, his former club.

McKinnon played four seasons with the Vikings before signing a four-year, $30 million deal with the 49ers in the offseason. He rushed for a career-best 570 yards last season.

San Francisco released three running backs earlier Saturday prior to the injury -- Joe Williams, Jeremy McNichols and Jeff Wilson Jr.

The 49ers currently have running backs Matt Breida, Alfred Morris and Raheem Mostert on the roster in addition to McKinnon.

Breida has missed the past three preseason games due to a shoulder injury. Shanahan said he will be available for the season opener.

San Francisco also released guard Jonathan Cooper and defensive end Jeremiah Attaochu on Saturday. Cooper received a one-year, $4.95 million deal in the offseason as a free agent, while Attaochu signed a one-year, $3 million pact.

(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)