Vince's trade value is in the dirt. You're out of the playoffs. Playing him is a smart move because you can possibly increase his trade value (it can't really get much lower, and optimistic teams can blame any struggles on the other problems), leading to more picks/players when he's gone at the end of the year. Or he could even tear it up and help you win a few. You're certainly not going to get a new defense or talented WRs right now. So looking at a 'new' QB is something that can be done, even if it's probably rearranging deckchairs.