I would trade him right now for whatever they can get and use the money in free agency. Signing Callahan for 6x6 is almost a guarantee to be an albatross contract. He doesn't fit this system, he's declining, and he's injury prone. Getting a 1st round pick for him, plus 1-2 free agents is better for this team in the long run. Now, the free agent signing(s) could very well turn out to be bad deals, but at least they would be leaving themselves open to get a productive player plus the first round pick (or whatever they get in return for Cally).