Hard to believe now, but another knock on him coming out was his athleticism. You obviously need the physical tools, but so much of being a successful NFL QB is between the ears. That's why Jay Cutler is Jay Cutler and Aaron Rodgers is Aaron Rodgers.
Good call, m'joe.
It's the exact same reason QB's like Vick, Culpepper, JaMarcus Russell, McNabb, and other QBs who can run ultimately fail. They can't read a defense. Arm strength and accuracy may or may not be there, but if they don't know where to throw it, they can't win games consistently by passing. They may have some success scrambling for big plays when one breaks down, but it tends to make their offenses one-dimensional.
Some other QBs are the opposite. They have the arm strength to make world-class throws, but can't read defenses well enough to win in the playoffs, if not in the regular season (**Cough, hack, Favre, cough**), Peyton, Rivers; even flakes like Ryan Leaf and Jeff George are good examples, as well. And they generally aren't as mobile, so if they struggle passing, they generally are doomed to suffer the same one-dimensional problem.