Theoretically he can, but it's not going to happen. If he has to stay for a year then the benchmark on how to act has just been set by Keita, with his comments about giving his all for the remainder of the season, at his club.
He might have acted the cunt, but it's in no ones interests for him to play shite and continue to act like a prick. He's got to walk out on the pitch and not give the fans a reason to get on his back, the only way to do that is to perform, and the only way to stay relevant to the Brazilian World Cup squad is to do the same. Him spitting his dummy out won't happen.
For once we do seem to hold the cards, he's either going for an extortionate fee in the next few days, or we keep him for a year and get the best from him and just get on with it. It's not ideal but it's the best of a shitty situation.
Personally I hope we keep him and agree a fee now, it's at least a compromise from both parties then, rather than us typically bowing down to a top player and the call of another footballing giant. I think he's an idiot for going there now, particularly the way we are playing, but if it's his dream, then there's not really alot we can do about it, other than get our moneys worth and make sure he goes at least partly on our terms.