If Brown really knows he just doesn't have it anymore then, like a lot of you guys said, he should really just retire. Save Yankee fans, and baseball fans for that matter, just more agony.
But I wouldn't drop the guillotine just yet. Keep an eye on Brown...a very distant eye. Wait for him to have two solid consecutive starts and for a reason why he would suddenly be doing better (i.e. noticably improved mentality, change in technique or training regimen, passing of previously unknown lingering injury, etc.) and then if you have a spot, I think he's worth a shot. Only because we all know what he's capable of.
But barring those circumstances (which indeed seem highly unlikely right now) STAY THE HELL AWAY FROM HIM.