You watch the film, you "scout" players, you interview the player - Sure, players with blue eyes are generally better Quarterbacks than players with green eyes, but at the end of the day, that's why they make them coloured contact lenses. Scouts are paid good money for a reason. They evaluate players and make a recommendation as to who is the better player based on their observation. I am an absolute whiz with spreadsheets and I have a college degree in mathematics majoring in statistics. I don't think that would qualify me for a job as a chief scout for an NFL team.