"I don't believe that you can be too short as a quarterback. It's not about height"

Drew Brees is suggesting that height is not an establishing factor in a quarterback's success. He thinks that a quarterback's success is based on their ability and capacity, not their height. He believes that a quarterback can be successful no matter their elevation. He is suggesting that a quarterback's success is based upon their capability to read the defense, make quick decisions, as well as accurately throw the round. He believes that a quarterback's height does not determine their success, which a much shorter quarterback can be just as effective as a taller one. He is highlighting that a quarterback's success is based upon their skill and capacity, not their elevation. He is recommending that height should not be a factor in figuring out a quarterback's success.