SANTA CLARA -- As the 49ers headed out to practice, starting defensive tackle Ray McDonald instead walked gingerly to his car. McDonald is wearing an orthopedic boot for a high, left-ankle sprain that likely will keep him out of Sunday's game at New Orleans.
Demarcus Dobbs and Tony Jerod-Eddie are candidates to replace McDonald, although Tank Carradine is an option if the 49ers opt to activate him for the first time his rookie season.
McDonald missed the second half of Sunday's 10-9 loss to the Carolina Panthers. He's started every game this season at left defensive tackle and all but one game over the previous two seasons.
Outside linebacker Dan Skuta also was wearing a compression boot on his left foot Tuesday, which likely means significantly more playing time for Aldon Smith, who played just 12 snaps Sunday in his return from a five-game absence.