We're at that point in the year again, where fall sports getting set to begin. It's a mad... no, MAD! dash to the first game. Coach Vern Gambetta's recent post, Preseason Practice – Where Championships Are Lost, is right on. I would agree that the fatigue and the injuries it causes is more neural than metabolic.
Plus to add to his statements, of too much volume of high intensity practices, heat and poor hydration, what about anxiety? Being a former athlete, I don't remember the start of any season not accompanied by some anxiety. The excitement and sensory overload just magnifies the metabolic fatigue. Anxiety leads decreased motor performance and decreased heart rate variability and all it's effects on performance, increasing fatigue. This goes right along with my previous post: Mindful Training.
The physical components play a role, but, again, the 'whole' athlete, and just as importantly, the context, cannot be overlooked. Great coaching awareness is a must.