Coaches cannot teach talent. What they can do is put players with talent in the best situation to maximize the talent. That is what Belichick did with Brady. Brady had the talent and Belichick nurtured it.
And let's face it, there is a chance that if Brady ended up on another team that he might not have even made it into the NFL or just languished on a team's practice squad for a few years and exited the league. In 2000, Belichick saw the talent in him and decided to keep a fourth QB that year to keep him on the roster, but another head coach may not have seen that talent and let him squander it.
lol ok only Bull can see if a QB not drafted in the first round has talent











