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Correlating Triple-A walk and strikeout rates to the Major Leagues

How does a prospect's minor league walk or strikeout rate correlate to his rate in the majors?

Introduction

As I began my series of correlating prospect walk and strike ratios to future hitting success, a question arose from Carson Cistulli. How do minor and major league walk and strikeout rates compare to each other? I did a little of this analysis in my original series at The Platoon Advantage, but never pursued it in any depth. Consider this a supplement to the already running series.

Previous Levels: Rookie and Short-A | Single-A | Advanced-A | Double-A

Method

I took the same data but instead split minor league seasons into various BB% or K% bins, basically the equivalent of Very Low, Low, Average, High, and Very High. Then I compared those rates with the player’s eventual MLB rate. If a player had fewer than 500 MLB PAs, I did not count his rate, since that is too small of a sample.

Hopefully the following tables are simple to understand, but just in case I didn’t design them well enough, I will explain. The first column contains the labels for BB% or K% at the minor league level. The second column contains prospects who had 0-499 PAs at the major league level. The third through eighth columns are the percentage of prospects that had that column heading’s major league BB% or K%. This means that rows add up to 100%, but columns do not.

Walk Percentage

Once a prospect is in AAA, he does not have a lot of developmental time left. This means his approach generally is what it is. While, as always, extreme approaches in the minors find a way to regress to the mean in the majors, some players are able to hold onto that extreme approach in the next level. Very few players stick around the major leagues with a walk rate below 4%. Of the players with 4% or lower walk rates in the minors, many find themselves failing at the highest level. However, if he is able to fine tune his eye enough and move up a notch, he has a chance of staying around with the big boys.

Strikeout Percentage

For prospects with extremely high walk rates, there are two options: Find a way to succeed while striking out in at least a fifth of their plate appearances or fail as a major leaguer. Many players are able to shrink down their total amount of strikeouts, but are still above the league average. Players with extremely low strikeout rates don't maintain them as strongly as their high K counterparts, but do have a much higher success rate.

Well, I've covered how walks and strikeouts correlate to major league hitting success for prospects. The final post in this series will wrap up all of my conclusions and provide correlations over a player's entire minor league career.

. . .

Statistics courtesy of Fangraphs and Baseball Prospectus.

Chris St. John is a writer at Beyond The Box Score. You can follow him on Twitter at @stealofhome.

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