They quite clearly failed their duty of care by allowing him to go back on the field and not receiving immediate medical attention required. He was quite literally minutes away from death.What happened then?
I'm not sure why you're so persistent in arguing that this is not a serious issue, just because the worst did not happen.
In any other workplace, when your employer puts you in serious risk of harm like this you 100% have a right to explore legal ramifications. The AFL is not immune to common workplace laws.