If Mac had failed the headlines would have been rookie chokes, Matt not good enough for Brady etc etc. Bill understood this and took it upon himself. Now rather than blame Mac for choking, or winning I guess, we get to criticize Bill for making the call. Pretty tough position to put a rookie qb in, early in his rookie season.
How much or how little does this impact a QB? A team? A coach? All very interesting questions with significant depth.
We are so enamored with the physical outcomes of being a QB, that we usually ignore or under-evaluate the mental ones when considering growth of a rookie. There are plenty of examples of QBs with all the physical gifts the world could offer, but they still weren't able to employ them either consistently or in the most crucial of moments.
Taking one of those moments in a rookie season, in possibly the birightest spotlight of that campaign versus the team's own former leader, and going to low risk route - can also be heavily debated with "if-then" statements. If he succeeded then...or if he failed then...
That's what I'm looking for out of this season, not number of TDs, or yards, but does he have the clutch aspect to do the right thing in pressure moments? Not EVERY time, but some of the time (more so than last year where there were very few of them - i.e the late TD strike to Bourne vs DAL)? Did having the ball taken from his hands in your Tampa game example light a fire...or was it just another moment?
In short, is Mac an elite...or just a borderline great QB (poor, average, good, great, elite)? He was a definitive good last year, sometimes great, but jury is still out as to "elite".