I would take a gamble on the Rook here and grab Crabs! He will either be a Boom or a Bust and I think he will "BOOM"!!!
Caldwell isn't spectacular and I think Crabs will eventually outproduce him fantasy point wise!
Take Crabs and if he doesn't work out I am sure Caldwell will still be available or someone else better will hit the FA market!
Standard H2H 12 Team 1 Pt PPR, Start 1QB, 2RB, 2WR, 1 FLEX (RB/WR/TE), 1TE, 1K, 1 DEF