One factor people seemingly look at when trying to predict which young players will become “all time greats” is their age upon reaching the major leagues. Today, many players people predict will become great (Porcello, Justin Upton, Felix Hernandez) are the ones called up at a young age.
I stumbled across the following table on baseball cube showing the oldest and youngest players baseball over the past 50 seasons. What’s interesting is how many players I did not recognize. I decided to experiment whether the average hall of famer is younger when called up to the major leagues because assuming “call up age” is factor in a player’s long-term potential, it would follow the average age that future hall of famers would be several years younger (I was guessing 21).
Surprisingly, the age of the average hall of famer enters the majors at around 23. The average age of a major league rookie is 24 years old. In other words, for whatever reason, there is little difference between the average age a hall of famer and non-hall of famer enter the major leagues.
I am not certain why there is little correlation between reaching the major leagues at a younger age and making the hall of fame. The obvious explanation is certain players are called to the major leagues before they are ready. On the baseballcube list, the best examples are David Clyde and Todd Van Poppel. Nevertheless, most of the players on this list (Fernando Valenzuela, Wilson Alvarez, Jose Rijo, etc) were all successful at an early age. My conclusion would simply be it’s much more difficult to track whether a young player will continue to be successful over the course of 15-20 seasons.
Note: the “average age entering the hall of fame” data might be slightly inaccurate for two reasons: (1) I created a spreadsheet which only got about half-way through the several hundred players in Cooperstown (I am willing to bet the average age of all players is about the same); and (2) I excluded players called up before 1903 (b/c “modern” MLB started with the World Series).