I agree with your OP,
@The Franchise. I think the process has already begun, as to this being Diaz first major test. From the outset, he set a "ridiculously high standard" (his words) for the QB's, on and off the field. As a result, we have already seen much improved and needed maturity from all three QB's.
From day one, he has been ****-bent on changing the culture and mental makeup of the team, especially the QB's. During the ACC media days, he mentioned that he felt the team had a weak mindset last year, in which it showed on the field. Manny's personality alone, has and will continue to play a huge role in changing the mental makeup of the QB's. Add in the hires, but more specifically upgrades of Enos over Junior, and equally as important, Feeley over Gus, and what we have is an environment that exposes and nullifies entitlement and selfishness, while simultaneously venerates and embraces accountability, hard work, and discipline.
Again, I completely agree with you. How Diaz handles this matter will have a huge positive or negative impact on the entire team. The good news is based upon what we've seen thus far from Diaz and his staff, we can feel a bit optimistic about how the situation will play out.