1. He didn't waste ANY, talk less 'a significant', portion of his career. He was a key young developing player for the first 3 years of his career here.
2. In the last year, he has become disfavored by the manager. For good reason, others have been better.
3. Based on the abive trajectory and the significant interest from other equally big clubs he doesn't see it as in his best interest to continue here.
Point 3 is so obvious, that even the thickest blue lenses shouldn't blind anyone.
4. As for what the club deserves from him. The club deserves a level of professionalism. Show up, do his job and don't be an embarrassment to the club outside. He has been all that. As for getting something back, the club doesn't "deserve" that. You get significant money back if a player wants to break his contract early or another club wants him badly after a few years.
However, if the player performs under his contract. That is all he owes the club. He is not from City nor did he come thru the City youth ranks. He was just a fantastic young player City bought from another team.
He hasn't become the key player he hoped to be, so he has to go try somewhere else. He owes us nothing. If we wanted more from him, we should have sold him the minute he did not re-sign.