See it's like I said, every character is reinforcing it, Ashito isn't injured he's just completely exhausted. This is something he will overcome in the next year or two before he becomes a pro. Odd that the coach is arguing he already had limitless stamina but he will ACTUALLY have enough stamina to play at this level for a whole match in another year or two.
As for the referee call, people are calling it bs super prematurely. The panel is deliberately drawn so you can't tell how dangerous the tackle was, it seems like a fair call to me, but it also could've been Xhaka deliberately using his reaction time to fake contact. Doesn't mean the referee is bad, if he saw it from the angle that the audience is shown it then 9 out of 10 refs would make the same call.