In addition to the physical things mentioned elsewhere, the Quarterback is the brains of the team during a play. They get the ball, and need to have very rapid situational awareness & risk assessments to choose who throw the ball to depending on where openings are appearing or not. This is very difficult.
The running patterns the receivers follow are pre determined, but who gets the pass is not. You need to determine, who is open, where will be they be in x seconds, will the defensive line hold or is someone going to knock you down before the pass, is there a good opening to just run for it yourself instead of passing, etc.
The running patterns the receivers follow are pre determined, but who gets the pass is not. You need to determine, who is open, where will be they be in x seconds, will the defensive line hold or is someone going to knock you down before the pass, is there a good opening to just run for it yourself instead of passing, etc.