Not up to pace of the Prem and too old.
No longer the player (but still the prick)
Red card waiting to happen (In April he was given 8 match ban for abusing a ref)
Would destroy dressing room morale
Fallen 'stars' chasing their youth,... with his personality, could only be a bad thing.
Dirty cheating Cnut that I would detest if he ever signed.
My first though was this was paper talk to help us get an alternative over the line, as who could take Costa to Everton seriously?? Then I thought well if it is believable, then it also must be possible. That's when I started to feel ill.