Cook is nursing a hamstring injury and Spencer has been bothered by a sore shoulder. Neither participated in practice on Friday.
Victor Butler is expected to start at linebacker for Dallas.
Baltimore places left guard Ramon Harewood on the inactive list, even though he started the first five games and is not listed on the injury report. The Ravens list Bobbie Williams as the starting left guard.
Dallas' other inactives are punter Brian Moorman, wide receiver Cole Beasley, safety Matt Johnson, linebacker Orie Lemon and defensive tackle Marcus Spears.
Baltimore's inactive list includes linebacker Sergio Kindle and guard Jah Reid (calf).