It's a little different in Taysom's case. It's not just what he physically does out on the field (there's nobody else that can throw, run, catch, AND block at the levels that TH can) it's also what he knows. He knows the assignments for EVERY skill position. That's why he's literally 1 of 1...like, ever.
Taysom IS the backup at QB, RB, FB, TE, and receiver. He doesn't have a backup, and he never will. Because of what he can do, and because of what he knows, he can be lined up anywhere to create a favorable matchup or serve as a decoy because he's explosive with the ball in his hands. When he's done, we'll likely never see anyone like him again.