I agree, he can do wtf he wants , we had the chance to keep him but chose not to.Sunderland fans thinking we feel shafted by that are simply wrong and they know it.
Whilst he could've signed the deal on offer, I'm sure the club were unwilling to even give an inch in attempting to keep him.
When he signed on 3 years ago he waa given assurances about improvements to the training ground, still nothing happened on that front. I doubt the club would see it as a priority.
As you say they've had a chance to keep him, but he chose to leave at the end of his contract as the club haven't made the efforts to entice him to sign.