Lindsey is going to have a role beyond this year and is a solid RB. Watkins is a nice WR3 to have with some upside. Cook is never on the field although much of this year's loss can most likely be contributed to cascading injuries from coming back from the ACL tear. Next year should be better.
If you need help this year then the Lindsey/Watkins side is the one. For long term outlook it's a lot closer and depending on the rest of your roster I could be leaning towards Cook. But I think it's really a coin flip.