Tennessee Code Title 20. Civil Procedure § 20-6-401

A co-maker or surety, when sued alone, may, with the consent of the co-maker's or surety's co-maker or principal, use, by way of setoff, any of the debts or demands, held by the co-maker or principal against the plaintiff at the commencement of the action, and matured when offered in setoff, but the plaintiff may meet it in the same way as if made by the co-maker or principal who originally held the debts or demands.