Tremayne Anchrum Jr.’s first career start was cut short on Sunday after he suffered a leg injury on the Rams’ second offensive play. He was carted off the field and quickly ruled out, and the injury is as severe as initially feared.

According to Ian Rapoport, Anchrum has a fractured fibula and will undergo surgery. He’ll be placed on injured reserve and sidelined indefinitely. Anchrum was filling in at right guard with Brian Allen out, so this injury leaves the offensive line even thinner than it was a week ago.

A.J. Jackson, who primarily plays offensive tackle, replaced Anchrum at guard and played the remainder of the game on Sunday. He’ll presumably remain a starter until Allen returns at center and pushes Coleman Shelton back out to his original position of right guard.