That would have been a good arguement to resign him before his contract expired, which they did. As many people seem to forget, with Dareus coming off an absolutely dominating year, they signed him to a market value contract to retain him. Bills fans rejoiced.
Unfortunately, he has been terrible since. He clearly has motivation issues, he is out of shape,and playing like a replacement level player at best. At his current level of play, they will do just as well with the JAGs they have been rotating in. Moving on from him at this current level will not cause the team to miss a beat. He is hardly any longer a "star player". I seriously doubt he has it in him to regain his once premier level of play, regardless of where he ends up.