We've already talked about Cadillac Williams several times. He's not a productive starting running back anymore, but he's a terrific blocker on third down as well as a great pass-catcher out of the backfield. He was consistently able to turn short passes into bigger gains, even converting a few long third downs with screen passes.
But that's not all, he also turned into an effective runner on third down. To be precise: he wasn't just a little bit effective, he was the most effective third-down back in the league, according to Football Outsiders' stats. He had 16 third- or fourth down carries, turned those carries into 166 yards and 10 first downs (63%).
This again highlights Cadillac's value for the Bucs. The more I think about it, the more I feel this is one player the Bucs have to re-sign. He isn't effective as a first- or second-down back any more, but he allows Josh Freeman to coordinate an efficient passing game on third down and in two-minute situations. Without Caddy, the passing game will take a significant hit.