I'd take him back, don't hate the guy.
At the time I could understand him for leaving BUT the thing that annoyed most is the club/manager he chose to join. Pardew is the devil and we knew it would end badly BUT it's unfair to expect him to have shared the same dislike we have for Pardew.
He thought he was doing the right thing, we knew it wasn't and we have proven to be right.
Rafa can get him back in form and that's the important thing, if Rafa is willing to sign him then he obviously understood why he wanted to leave and he would have done it in a respectful way.