San Francisco 49ers tackle Shon Coleman went down early during Saturday night's preseason opener against the Dallas Cowboys with what looked like a serious injury to his lower right leg. The offensive lineman was carted off the field with an air cast placed over his leg.

The 49ers later reported the injury as "an ankle injury" and Coleman was ruled out for the remainder of the game. General manager John Lynch didn't sound too optimistic about Coleman's condition while speaking with Greg Papa and Tim Ryan during the broadcast.

Matt Barrows of The Athletic reports that Coleman will receive an MRI tomorrow but the injury is already believed to be a season-ender.

Shanahan was asked after the game if he had any more information on the injury.

"No," he responded. "I saw what you guys saw, though. It looked serious but I don't know yet."

Coleman was competing for the swing tackle job behind starters Joe Staley and Mike McGlinchey. San Francisco could make a move before the start of the season to acquire another tackle. It is also worth noting that the 49ers are No. 2 in priority when it comes to claiming players off waivers.

The 49ers traded a 2019 seventh-round pick to the Cleveland Browns for Coleman on August 31, 2018.