Arizona Cardinals running back Chris Johnson left Sunday's game against the San Francisco 49ers with a knee injury and is questionable to return.
Running back Andre Ellington is also questionable to return with a foot injury.
Johnson was worked on by the Cardinals' training staff before walking back to the locker room during the third quarter.
Shortly after Johnson left, Ellington injured his foot and was attended to on the sidelines by trainers. The Cardinals are down to rookie backup David Johnson.