The term "late bloomer" is used to describe an undersized and underdeveloped player who is athletic and gifted but for various reasons -- where he resides, the high school he attends, the offensive or defensive system he plays in -- was overlooked by many college recruiters. This can be particularly true when it comes to quarterback play.
Every coach would like to have upside and potential in his prospects. A prospect with ability and a ceiling that has yet to be reached is what makes coaching fun and challenging. However, rating performance vs. potential always has been a challenge in terms of making scouting decisions -- or, more importantly, scouting errors.
Statistics, system, level of competition and experience are all factors in evaluating quarterbacks at all levels of football, from high school to the NFL, but statistics and system may be the most misleading in projecting future success.