The other thing Mac has going for him is that he is being developed by the same guy who developed Brady. And I don't mean Tom House (although that's cool) but Bill Belichick.
It was not **** Rehbein, nor Charlie Weis, nor Josh McDaniels, nor Bill O'Brien, nor some lowby QB coach that developed Brady, it was Bill Belichick.
I'm sorry to disagree with all the Brady worshippers here, but 20 years of film review and game planning sessions with Belichick had to have been crucial in Brady's taking his game to the GOAT level.
Brady's the GOAT, and Mac has not even proven he's an NFL franchise QB yet, but both of them share a lot of attributes, and a very important similarity is that they are both phenomenal working learners.
And as we can see already from the OTA's, Belichick is teaching Mac, too. Mac sadly won't have 20 years with Belichick, but I suspect that Bill is committed to giving him a PhD level crash course in playing QB in the NFL at the highest level.