They can tag him, and still allow him to seek offers elsewhere. Then, they can either match or negotiate a deal to give the other team the power to sign him. Doesn't have to be two first rounders. I'd say a tag is plausible, as that 12.5 guaranteed salary can just become part of the signing bonus that's sure to be well north of that amount anyway.

The fact that Cobb is not tagged leads me to believe a deal is imminent, but it's not proof positive, obviously.