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Forecasting Royals Prospects Using KATOH

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Crystal LoGiudice-USA TODAY Sports

Just prior to the turn of the calendar, Chris Mitchell of relative Hardball Times fame released the results of his KATOH forecasting "system." Said system is named after Gosuke Katon (a Yankees "prospect") and seeks to find some meaning in a minor league baseball players age and stats in relation to his long term prospects of playing in the major leagues.

If you're interested in the methodology of the endeavor and further explanation and reasonings then I suggest reading the entire article, but below is a primer of sorts:

To get a better sense of what mattered most, I turned to the reams of minor league data available through Baseball-Reference. Using these data, I ran some probit regressions, which tell us how a variety of inputs can predict the likelihood of an event that has two possible outcomes. For example, it might give the probability of a prospect's making it to the majors based on his age and league-adjusted strikeout percentage, walk percentage, isolated slugging, batting average on balls in play, and frequency of stolen base attempts....

First, I took all hitters who played in the majors and had a KATOH projection from 1990 or later and assigned them to the position at which they played the most innings through age 28. From there, I looked to see how players from each position performed against their projections. Considering only major leaguers created some selection bias: A player who has made it to the majors is more likely than a randomly selected player to surpass any WAR threshold. So to tease out this factor, I adjusted the data in the table below to refer to each position's performance relative to the average major leaguer.

Again, I suggest you do read the entirety of his article because it does show some interesting thoughts (such as the predication and correlation of walks to possible major league success in the low minors). Regardless of your decision, we're going to look at how this study forecasted Royals prospects. One should note though that the KATOH system exclusively only considered hitting prospects for it's "success forecasting" (my own term, not Mitchell's) in this release.

What I've done is collected any hitters on that list that A) are in the Royals organization and B) can be in some way considered a prospect or bear some resemblance of prospectdom.

Name Age MLB >4 WAR >6 WAR >8 WAR >10 WAR >12 WAR >16 WAR WAR through age 28
Marten Gasparini 17 39% 36% 36% 34% 30% 29% 29% 8.0
Raul Mondesi 18 76% 34% 26% 25% 25% 25% 18% 6.8
Cheslor Cuthbert 21 88% 40% 29% 23% 18% 16% 8% 5.7
Elier Hernandez 19 67% 20% 15% 12% 12% 12% 7% 3.9
Chase Vallot 17 32% 17% 15% 13% 11% 11% 11% 3.5
Samir Duenez 18 50% 16% 11% 9% 9% 9% 6% 2.9
Lane Adams 24 72% 11% 7% 5% 4% 3% 2% 2.4
Christian Colon 25 80% 14% 4% 2% 1% 0% 0% 2.2
Whit Merrifield 25 72% 7% 3% 1% 1% 0% 0% 1.8
Terrance Gore 23 16% 8% 7% 6% 6% 6% 6% 1.8
Dominique Taylor 21 42% 7% 4% 3% 3% 2% 1% 1.4
Bubba Starling 21 40% 7% 4% 3% 2% 2% 1% 1.4
Orlando Caxito 22 49% 4% 3% 2% 1% 1% 0% 1.3
Jorge Bonifacio 21 48% 4% 3% 2% 2% 1% 0% 1.3
Alexis Rivera 20 37% 7% 4% 3% 2% 1% 1% 1.3
Ramon Torres 21 35% 4% 2% 2% 1% 1% 1% 1.1
Hunter Dozier 22 38% 5% 3% 3% 1% 1% 0% 1.1
Frank Schwindel 22 33% 4% 3% 2% 2% 2% 1% 1.1
Cameron Gallagher 21 30% 5% 2% 2% 1% 1% 1% 1.0
Humberto Arteaga 20 30% 3% 1% 1% 1% 1% 1% 0.9
Ryan O'Hearn 20 22% 3% 3% 2% 2% 1% 1% 0.8
Brett Eibner 25 39% 1% 0% 0% 0% 0% 0% 0.8
Zane Evans 22 22% 2% 1% 1% 0% 0% 0% 0.6
Paulo Orlando 28 32% 0% 0% 0% 0% 0% 0% 0.6
Cody Stubbs 23 16% 1% 1% 0% 0% 0% 0% 0.4
Daniel Rockett 23 9% 0% 0% 0% 0% 0% 0% 0.2
Corey Toups 23 3% 0% 0% 0% 0% 0% 0% 0.1

Anything surprising here? I'm not sure there's anything worth really looking at...oh...wait...I guess Marten Gasparini (a 17 year old with just 23 games in Rookie Ball) is the best forecasted player under this system. Gasps is perhaps the best prospect to ever come out of Europe, or at least one of the best, but most would argue that there are names on the list above who's prospectdom is greater. Now, that isn't necessarily the goal or point of the system (identifying who is and who isn't a prospect and where to rank them), but it is curious.

For instance, here is Marten Gasparini along side Dodgers prospect Corey Seager:

Name Age MLB >4 WAR >6 WAR >8 WAR >10 WAR >12 WAR >16 WAR WAR through age 28
Marten Gasparini 17 39% 36% 36% 34% 30% 29% 29% 8
Corey Seager 20 88% 43% 39% 37% 31% 29% 17% 7.9

KATOH likes Seager's future prospects of appearing in the Major Leagues more than twice as much as Marty's which makes sense given that Seager just completed a highly successful AA campaign as a 20 year old. Once past the MLB expectation column, KATOH likes both players nearly equally in regards to WAR forecast.

Both prospects are younger than their league average age and while Gasparini is expected to remain at shortstop for the long term, Seager faces not necessarily a non-zero chance of remaining there, but it's low. That's really where the comparison ends.

Truthfully, Seager is a much better prospect. The three major prospect pundits (Baseball America, Baseball Prospectus, and MLB.com) all ranked Seager in the top 50 of their overall list last offseason and BP ranked Seager 19th overall in their July midseason list. Meanwhile, it would be surprising likely if Gasparini made even the Royals top 15 list, let alone an overall top 50 list like Seager.

Mitchell himself has admitted that KATOH is not great at predicting players in the low minors and Gasparini played in nearly the lowest of all low minors. What KATOH probably likes about Gasparini is his age relative to league, his ability to steal bases (6 steals in 23 games), and his defensive position.

Other notes:

I think I'll buy the Mondesi forecast for probably all the columns. There's a reasonable chance Mondesi appears in AA in 2015, and playing in AA as a ~19 year old generally bodes well for future success. That list includes players such as Jurickson Profar, Manny Machado, Bryce Harper, Mike Trout, Jason Heyward, Starlin Castro, Freddie Freeman, Giancarlo Stanton, Elvis Andrus, and Justin Upton. Now, this is not to say that Mondesi will be as or nearly as good as those listed players, but Mondesi has the pedigree of a pretty good prospect much like most of the listed players.

I'll take the under on Cuthbert. I'll talk more about him in my top 30, but given the profile I see, I think nearly 6 wins 5 years or so from now isn't likely to happen.

Much like the future discussion I'll have about Cuthbert, the Elier Hernandez forecast also surprises me. It's a different situation than Cheslor, and I don't think 3.9 wins is necessarily high, but out of the list I don't think I'd forecast him as the 4th best player there.

I know I'm just continuing this meme by mentioning it, but I'll take the over on Dozier for the age 28 win value. Despite his struggle in AA, Dozier has hit admirably in his previous levels and there's reason to believe he's roughly a league average defender at third base. If he were to be able to produce a ~100 wRC+ with average defense at 3B then he could be a ~2 win player per season. Also one must argue that Dozier's prospectdom is higher than Frank Schwindel, Cam Gallagher, and Ramon Torres. Players all forecasted to produce roughly the same value through their age 28 season.

Mitchell plans to release a KATOH forecast for pitchers at a future date. My contract with Royals Review legally demands that I cover that release as well.