Tenacious O
Part 1 of A New System for Evaluating Prospects (01/21/02)

This is the greatest and best song in the world... Tribute*

The process for evaluating talent in baseball is the most advanced and scientific of any sport.  Not only does it incorporate the insights of seasoned observers, but it includes a wealth of data in the form of statistics.  Unfortunately, as advanced as the process is, relatively speaking, it's still rather medieval.  Just like science in the middle ages, it's still a complex mixture of rudimentary scientific method and religious dogma.  For example, we often look at strikeout-to-walk ratios for pitchers in hopes of finding the next Greg Maddux.  Yet we still drop our pencils and worship the sight of a 98-mph fastball, regardless of how far from the plate it ends up.  And we routinely ignore pitchers with great control ratios, but who couldn't break glass with their #1.

Baseball scouts are first and foremost, judges of talent.  They will tell you that a player who can accomplish certain physical feats - throw a 98 mph fastball for instance - at a young age will much more likely develop into a major league player than one who first accomplishes the feat at an older age.  But that doesn't necessarily mean that player will become a major leaguer.  It takes more than talent to make it to the show.  Talent, and the skill to use that talent effectively, is what is required to become a major league player.  However, with younger players, that skill is still being developed.  Without the obvious developed skill, a player with an abundance of talent can sometimes be confused, at least statistically speaking, with a player who has an overall lack of it.  It is here where a player's age gives us an important clue.

Look into my eyes and it's easy to see one and one make two, two and one make three... it was destiny

Last year, I completed a study on the relation between a player's age when he makes his major league debut and the quality of his major league performance.  I used Total Player Rating as my statistical measure because, at the time, it was the only complete statistic that gave an evaluation of the player as a whole, regardless of whether he was an everyday player or a pitcher.  Once I become familiar with Bill James' new Win Shares statistic, I will run a similar study using it, to see if any discrepancies develop.

Granted, using a study based on TPR might be dicey, as controversial as TPR is.  However, the questions concerning the validity of TPR stem from it's ability to evaluate individuals.  That should not effect it's value in a global study like this one.  The sum of the TPRs of all players is zero, because the history of wins and losses is already fixed; all TPR sets out to do is to assign credit or blame.  Any individual anomalies would be washed out in the sheer volume of the sample.

Anyway, in this study, I listed every major league player in history by the age at which he debuted, along with his career TPR, then averaged the TPR by each debut age year.  The study showed that, on average, hitters who made their major league debut between the ages of 18 and 22 were the most productive hitters.

Debut Age Average Career TPR Debut Age Average Career TPR Debut Age Average Career TPR
16  -2.36 20  1.72 24 -0.89
17   -0.04 21  1.32 25 -0.98
18    2.34 22    0.18 26 -1.08
19   4.11 23  -1.01 27  -0.68

Minor league player evaluation is dependent on two factors - age and performance.  Performance has been the easy part to evaluate - one just has to look at the statistics.  However, age factor has been rather ethereal.  A player may have a sub par year statistically, yet still be considered a top prospect because of the age of his competition.

But how can one express that discrepancy in terms that will directly relate to the statistical record?  To date, even the best evaluators are left with saying things like, "I just have a gut feeling about this guy", or adding points for age in a ranking system that doesn't really give us a clue as to what to expect.

This is not the greatest song in the world... this is just a tribute

What I propose is to distill a hitter's age into a multiplier, much like park factor, that could be used to adjust any hitter's real statistics in order to demonstrate what we should expect from him once he reaches maturity in the majors.

Not only will hitters be compared to their peers age-wise, but they will also be compared to the optimum ages for their level.  That is, their age will be compared to the age necessary to get them to the majors by the time they are 22 years old, which, according to the TPR study, is the latest the average impact hitter makes the majors.  The optimum ages are:

AAA - 22 (a September call-up after the AAA season ends qualifies as a debut)
AA   - 21
A+   - 20
A    - 19

Last year, the average age in AAA was 27, which was a little more than 2 years younger (29.4) than the average major league player .  In AA it was 24, A+ was 22 and single A was 21.

In order to separate hitters who are optimum age as opposed to above average age, we divide the league average age by his actual age, then multiply that by the result of dividing the optimal age by his real age.  So players who are younger than both standards will gain added benefit, while those of above average age, but not under optimum age will see their production value decreased.

Age 30 in AAA = (27/30)*(22/30) = age factor of 0.66
Age 25 in AAA = (27/25)*(22/25) = age factor of 0.95
Age 21 in AAA = (27/21)*(22/21) = age factor of 1.35

Just like using park factors to adjust the performance of players give us a better idea of their true value, using the age factor will give us a better idea of what kind of performance to expect once the players reach maturity in the majors.  Unlike MLEs, which draw a comparison of what the player did the previous year with what he might have done in the majors the previous year, the age factor, or AF, will show what a player might be capable of once his body fully develops and he gets comfortable against major league competition.  And that, after all, is what we are trying to determine when we are evaluating minor league players.

And the peculiar thing is this, my friends - the song we sang on that fateful night, it didn't actually sound anything like this song... this is just a tribute

I have compiled a list of the 199 best hitters in the minor leagues last year.  I will offer a similar list for pitchers in the next week or two.

I only used full season minor league players for several reasons, the two most significant were sample size, and, more importantly, player ages.  Players find themselves in rookie ball for a number of reasons: very young players, injury rehabs, an organizational philosophy to put new signees there to better gauge their talent, low-potential players, etc.  One simply does not get an accurate read on ability when using these short season leagues.

Only hitters who were eligible for major league rookie of the year in 2001 (less than 130 MLB at bats or 45 MLB games) were included.  Each player's season was condensed into a single statistical line, regardless of how many levels he appeared.  The base statistics (hits, ABs, HRs, etc) were added to give the single stat line.  The runs created for each level, however, were adjusted for ballpark and relative age - both in terms of the competition and the optimal debut age - before incorporating.  There are several players - Adam Dunn, Carlos Pena, Corey Patterson, etc - who were also included even though they had a signficant amount of playing time in the majors because they were eligible for RoY at the beginning of last season and played an equally significant amount in the minors.

The final rankings are based on an adjusted form of runs created, incorporating the age factor (column 3) and the park factor (column 4), and adjusted to 550 at bats.

The Best Minor League Hitters of 2001

...continued in Part 2: the pitchers

* - Before Jack Black became a household name - well, he's not exactly a household name yet, but he's well on his way - for his roles in movies like "High Fidelity", "Shallow Hal" and "Orange County", he was the lead singer and rhythm guitarist for a band called Tenacious D.  One of their most notable and radio-friendly songs is a tune called "Tribute".

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