The problem is that as long as TH plays here, he will never be a 1400+ yard running back. As long as he's a Bill, he'll be getting 2-5 carries per game to help out McGahee.
We didn't trade a great running back, we traded a malcontent who didn't want to be here and was only going to be a problem behind the scenes. TH didn't have much value to the Bills anymore.