Davis is a rookie. Both Davis and Johnson pass block better, Johnson is our 3rd down back. So to counter your argument, why wasn't cook on the field the last drive of the AFCCG? Because he isn't the best pass catching back.
Also, it took Cook 17 games just to barely break 1000 yards, and that isnt good.
He isn't worth it. The draft is loaded with guys who could start, and I still say Davis can start and do well in this league.