Sorry to jump in, but my sense of sensibility is taking over. You cited two examples of young players who suffered career-ending injuries, which is irrelevant to your point that Barkley mustn't be over-played. Neither player had to retire due to too many games - they both actually had less playing time than most others their age and were just unlucky enough to get badly injured. Barkley suffered a bad injury, but one that he has now recovered from - something neither of your examples did.
However, I'd agree that Barkley shouldn't be in the starting XI every week. A seventeen year-old is more susceptible to psychological fluctuations, especially if they have a dip in form. This can have a detrimental effect to their development. It's probably better for now if he doesn't think he's automatic first choice. Still, Rooney (a freakish exception, admittedly) finished his first season at 17 having made over 30 league appearances. Barkley has a similar bullish confidence to his play, and seems much better equipped, both physically and mentally, to deal with the pressures of being a first team regular.