The other thing Diego isn't and that's the finished product.
Picture this, a manager asks you to be ready to support other members of your team, it might involve helping a defender, a perfectly reasonable request I'd have thought. Yet the response the manager receives from the player is an objection to this request. Does this bode well for the future? Does it suggest that the player will pick and choose which instructions to follow? Should the player be given special dispensation because he's the 'special one', and knows far more than about the tactical demands of the game than several experienced coaching staff?
Compare the respective merits, a 19-year-old player, an exciting prospect, but unproven and with so much to learn. Then we have a coaching staff, varying experiences, highly knowledgeable about football. Their lives are based on improving the players they work with, and all they expect is for their players to listen and follow their instruction. They, the coaches, appreciate that not everything will work, but this is a part of educating young players. They, the young players, have to be prepared to try new ideas, ways of playing that will improve their game as well as that of the team.
Diego may be talented, but none of this tells anyone whether he's prepared to listen, learn, and become a far more rounded and better player. What's been described in the previous post wasn't designed to harm Diego as a player, in fact it was meant to improve his overall awareness of the game as a whole. Diego chose to reject this advice, and in doing so informed those coaches who are far more experienced than the young lad that there's an attitude problem.