the game is all mental and if you're bright you can work around your limitations/"flaws".
Manziel, Baker, and Kyler aren't in the same ballpark as how Bryce sees the game/field. Brees was. Russell is. that is why they thrive.
if you're 6"3 and a doof it doesn't matter if you can sling it or not. yes, putting on weight is important to prevent injury, but none of that will make him a better "football player."