Who is the best young player in baseball? A deceptively tricky question, in that it requires us to combine two unlike factors -- youth and talent -- into one measurement. C. C. Sabathia is certainly a better pitcher right now than Felix Hernandez, but Sabathia was 26 in 2007; Hernandez was 21. Does Hernandez' youth outweigh Sabathia's production? Alex Rios is probably a better player right now than Jeff Francoeur, but Francoeur is three years younger. Both players are 1) clearly still young, and 2) clearly very good. How do you balance Francoeur's additional youth against Rios' additional accomplishments?
You just have to pick a method and roll with it. We're not talking here about prospects or minor league players. We're discussing proven major league players who are still young. This was my method, in short. First, I eliminated from my study all players who were 29 years old in 2007 or older, since 29-year-olds in 2007 are now 30, and 30-year-old baseball players are not young. A 28- year-old player can be considered to have a little bit of youth left; a 30-year-old, no way. Second, I figured the runs created by each player -- for Rios, 105. Third, I made a "speed adjustment", since speed correlates strongly with defensive value, and defensive value is more difficult to measure. Fourth, I divided that total by the runs scored/runs allowed per game by the player's team, thus building in context adjustments. Fifth, I multiplied that by the number of years the player had left before he was 33 years old. For Alex Rios, this creates an output of 216, which ranks ... well, I'll get to that in a moment. For the pitchers, I developed a similar method based on runs allowed.
Why 33 years old, rather than 30? I tried it the other way and it doesn't work. Suppose that you have a 27-year-old player and a 24-year-old player of the same accomplishment...Jose Reyes and Albert Pujols, or Justin Verlander and Josh Beckett, or Edwin Encarnacion and Felipe Lopez. The 24-year-old is more valuable, and we want him to rank higher, but he's not twice as valuable. If we subtract his age from 30, that's 3 "years left" for the 27-year-olds, 6 years left for the 24-year-olds. It causes moderately good 22-year-olds to vault ahead of MVP-level 27-year-olds. Subtracting from 33 flattens the slope, creating better balance.