Good communication demands that we listen to each other. When AJ was having difficulty with Coach Kill, there must not have been a good understanding by the staff that AJ was suffering. Instead, it became a issue of control, football, and discipline, which are not at all helpful to a suffering mind. In fact, they can be counter productive.
Stress challenges the body both physically and emotionally. Often the body's store of energy and chemical resources are spent in handling stress. Football is one of the perfect stress factors that mankind can come up with. The nature of the game puts the body and the mind under duress unimaginable to many. Just the inflammation alone in the body is cause for concern, but the impact on the gut (the body's largest emotive center with the largest consumption of serotonin and other feel good chemicals by a factor of 30 over the brain) can cause immediate depression and anxiety in the body. Any damage to the gut can release an overload of chemicals causing mental confusion, cause depression, and cause inflammation around the Enteric system, adding internal communication problems back to the brain.
Broadly speaking, the coaching staff need to be aware of the mental health of their players and minimize stress so players can better cope with stress.
And, when a player reacts like AJ, it is a clear signal they need help and don't need additional 'stressers'.
What led up to AJ leaving the team is water under the bridge. But, how the team moves forward and learns from the experience matters. I think Coach Kill should take a page out of his own mental health playbook and practice it in the team. There is no need for the sport to be a plague of mental health issues or even miscommunication.
All you need to do is listen and observe.