There isn't a age as such but let me ask you, what age do you think you should be mature enough to handle the booing, criticism, standing on a pitch with 50000 ready to call you a twat. I have played football at a much lower level and it gets to you even if it's only a few hundred. I'm not defending him, he has work to do, but most of what he gets is unfairHe's not a kid though is he. At 21 I'm sure there are many of us who were married, had our own kids and were working more than one job to make ends meet. I understand that we don't all mature at the same rate, but saying someone is still a kid at 21 doesn't cut it for me.
Gen question for you. At what age does he stop becoming a kid and wakes up the next morning, an adult?