Offensive lineman Marcus Martin, who started the 49ers’ first 14 games, sat out another day of practice Thursday due to a concussion he sustained on Sunday.
Martin must pass all phases of the NFL’s concussion protocol to be available for Sunday’s game against the Detroit Lions. Martin must return to non-contact football activity and be cleared after undergoing contact simulation.
With Martin’s availability in question, the 49ers would likely start Sunday how they finished last week’s game against the Cincinnati Bengals – with Daniel Kilgore at center, Eric Pears at right guard and rookie Trent Brown at right tackle.