Arm Strength is for Suckers

I have been watching NFL Football my whole life, and much of that was spent watching great quarterbacks such as Montana and Young. I have devised a new formula for predicting quarterback success. This formula is meant to purposely downplay such traits as arm strength, height, passing accuracy, and other factors. Basically, once a QB reaches the pro level, it's not minor variations in arm strength that correlate with success. Instead, I propose these factors:

1. Backing up a veteran QB for 2-3 years. This time is spent practicing, understanding the offsense, and building confidence and maturity. QBs who just jump right in seem to struggle mightily.
2. Being tough. Good quarterbacks are tough and have no fear. You don't have to be the fastest guy to scramble for gains, but you have to be tough as nails and unafraid.
3. Establishing comeback potential. Once everyone believes that you can put up points in a hurry, two things change. First, the defense plays you differently. Second, your guys don't give up on you.

I assert these are the three measures of a QB that best predict success.