BPro Relative Draft Age Article: What does it mean for the Giants?

I pointed this out in Fla-Giant's thread about the AFL and AIL, but I decided to do a separate FanPost on it.  Last week, Rany Jazayerli of Baseball Prospectus and Grantland posted a two part article titled "Starting Them Young."  Part one is here and part two is here.  If you are interested in prospect development at all, I highly encourage you to read the articles.  They are very well thought out and very informative, and even though there's a lot of math in the middle, the conclusions are very interesting and could be very important.

Jazayerli comes to many conclusions over the course of the two articles, some of the most important of which I will block-quote below:

Let me repeat that: a team that drafted one of the five youngest high school hitters selected among the top 100 picks could expect MORE THAN TWICE AS MUCH VALUE from him as a team that selected one of the five oldest high school hitters. And that’s not a small sample size fluke; that’s a result derived from 32 years of the draft, looking at 160 players from both camps.

The other thing the chart reveals is that the five-year return for the oldest players in a draft class has been at or below 0% in every year of the study. There has never been a time when old high school hitters generated a positive return.

This is, all modesty aside, quite possibly the most impressive and significant finding of my career. When it comes to the drafting of high school hitters, even slight differences in age matter. At least when it comes to high school hitters, young draft picks are a MASSIVE market inefficiency.

We can safely say that the youngest 20 percent of high school hitters in any particular year will return, on average, about double what the oldest 20 percent of high school hitters will.

In other words, a 17-year-old player drafted #100 overall has as much expected value as an 18-year-old drafted #24. If a player who might look like a third-round pick on talent alone happens to be a full year younger than his draft class, he ought to be considered a late-first-round pick.

The difference in value between a player born in, say, October and in April is the difference in value between the #100 pick and the #43 pick, or the difference between the #30 pick and the #18 pick.

The article is free to non-suscribers, which I why I feel ok with copying such large tracts of text.  There's a ton of other good stuff there, so I would encourage you to read it if the nuggets above piqued your interest.

This is all well and good, but the question we all want to know is "how does this affect the Giants?"  In an effort to answer that question, I went back through every Giants draft since 1990, looking at high school hitters drafted in the first 30 rounds.  In actuality, from 1990 through about 2002 I could only look at players drafted in the first 10 rounds, since Baseball-Reference doesn't have birthdays for draft picks after the 10th round for that time period.  I ended with 27 players the Giants have drafted since 1990 that fit those criteria.

My first impression of the data is that, for the majority of this time period, the Giants shied away from high school hitters in the draft.  Since 2007, the Giants have drafted (and signed) 10 high school hitters; in the 17 years before that, they only drafted and signed 17.  My second impression?  The Giants' management of old really stunk at drafting high school hitters.  From 1990 to 2007, the best high school hitter management drafted and signed was Travis Ishikawa (drafted in 2002, career 0.9 rWAR).  The best high school hitter they ever drafted was J.D. Drew in 1994, but of course he didn't sign.

*Late addition:  Stumbled over this bit of awesome while researching this post.  Tony Torcato, who the Giants drafted in the first round in 1998 out of Woodland High School, is nearly two years younger than Andres Torres.

In part two of his article, Jazayerli splits his data set into five "buckets."  I'll spare you the gory details, but he describes each draft pick as either Very Young, Young, Average, Old, or Very Old.  Using his same constraints, I grouped the Giants' draft picks into these buckets.  Since 1990, the Giants have drafted 5 players Jazayerli classified as Very Young, 5 who were Young, 6 who were Average, 4 who were Old, and 7 who were Very Old.  That, in hindsight, isn't great draft strategy.  The oldest player drafted in the set was Wendell Fairley, who was 19 years and 73 days old when drafted in the first round in 2007.*  That year, the Giants actually used three first-round picks on high school hitters, the other two being Nick Noonan and Charlie Culberson.  Perhaps not surprisingly, those two have turned out to be better prospects than Fairley, at least thus far.

*Note: Just as Jazayerli did in his article, I standardized "draft day" as June 1st of each year, to maintain consistency.

The good news for Giants fans is that the organization's mindset seems to be changing.  In 2009, the Giants took high school catcher Tommy Joseph in the second round.  At 17 years, 320 days old on draft day, he qualified as Young, and thus far he has performed.  In all likelihood he will rank among the Giants' top 5 prospects, and certainly among the top 10.  The following year the Giants drafted Chuckie Jones in the seventh round, another draftee who classified as Young.  He struggled this year in Salem-Keizer, but he still shows lots of promise and it is certainly too old to give up on him yet.  This year, the Giants drafted and signed two high school hitters from Puerto Rico, Christian Diaz and Jean Delgado.

All signs seem to point towards a shift in the management's philosophy about high school hitters, which, according to Jazayerli's research, is a good thing for the organization.

Comment starter: What do you think of Jazayerli's article?