What Do Minor League Walk and Strikeout Rates Tell Us About Prospects: An Update

Introduction

Last year at The Platoon Advantage, I wrote a series of articles looking at walk and strikeout rates for former prospects. Carson Cistulli was kind enough to invite me onto FanGraphs audio to talk about these articles, which pushed me to dig deeper into the data. Eventually, I would like to completely redo this study, taking into account a few more factors, but for now I will just reuse the original data set.

As I said to Cistulli, any good research has its roots in fantasy baseball. This post is no exception, as George Springer, one of the prospects on my dynasty team and a prolific strikeout guy, was the launching pad of the idea. According to my preliminary findings, high strikeout players (like Springer) are almost always busts as hitters. However, I only looked at walks and strikeouts on their own. What if I combined the two and instead looked at prospects who walk and strikeout a lot? Home runs aren't a factor here, but you could call these the three true outcome prospects. How well do they do?

Method

The full description of my method can be found on the Rookie and Low-A post in the series. In summary, I used only Baseball America lists from 1990-2006 and found each prospect's walk and strikeout rate compared to the league average for that year. A prospect needed 150 plate appearances at each level to qualify. Then I determined if they became a productive, average or busted major league hitter using Fangraphs Batting Runs and a minimum of 1,500 Major League plate appearances.

Finally, quoting from the original article: "This distinction leads to three very important statistics: 21%, 21% and 58%. That's the percentage of productive, average and busted hitting prospects, respectively. Of course, this ignores defense and position, which may be where a player's value lies."

So the average hitting prospect will be productive 21% of the time and bust 58% of the time. We can compare these with the percentages at various walk and strikeout totals to see if they help or hurt the hitter's chances.

High walk and strikeout rates are all relative to the league and the year, but here are some general guidelines to help when deciding the type of player:

Results

For the total row, I removed all duplicates of players in multiple leagues. For example, Jack Cust had high walk and strikeout rates in High-A, AA and AAA, but he only counts once as a productive hitter (2,500 PAs of a 0.360 wOBA ain't bad).

The results are very similar to the old ones, but there are a few distinctions that were the very purpose of this study, in particular the final three columns. I originally found that high strikeout players had a higher rate of being busts than other players, but that changes dramatically when combined with a high walk rate. Only 13% of high K prospects succeeded without a high walk rate; 33% succeeded with one. 76% busted without a high walk rate; 50% did with one.

Which high strikeout prospects had productive major league careers with the bat?

More of the top productive players had an average walk rate with their high strikeout rate because that is more common overall. However, of those players with a high walk rate and high strikeout rate, a greater percentage of them became productive.

The high productive percentage for low BB, high K players in AAA is a small sample size mirage. Only six players qualified and two (Juan Gonzalez and Glenallen Hill) became productive.

How do more current prospects compare in these categories?

Check out this spreadsheet which looks at the success of 2006-2013 minor league prospects

Here are some highlights:

Mike Trout rated in either the High/Low or High/Avg categories in every level of the minors.

Domonic Brown was High/Avg in AA and Avg/Avg in AAA.

Yasiel Puig was Avg/Avg in AA.

Byron Buxton so far has placed in the Avg/Avg and High/Avg columns in Rookie and A-ball, placing him with prospects with a higher than average rate of success.

Carlos Correa was Low/Avg in Rookie ball which is not good, but is in the High/Avg category in A-ball with Buxton.

Bubba Starling was High/High in Rookie, but his walk rate has dropped so far in A, downgrading him to Avg/High and severely hindering his chances of becoming productive.

Hidden gems in the High walk categories in AA and AAA:

Of course, some of these players may be part of the 50% bust category, but they should at least get a shot to prove themselves in the majors.

Summary

This analysis is not the be-all and end-all, but it does provide a baseline for our expectations on prospects. It certainly helps us better understand George Springer. Without it, we would assume a much higher likelihood of him busting due to his high strikeout rate. However, when we take his high walk rate into account, his strikeout rate does not look as bad. When it comes to looking at a prospect's offensive capabilities, we should look at talent first (this analysis only included top 100 prospects), then walk rate, then strikeout rate.

As I've said before, becoming a successful prospect means adapting. Without this, pitchers will find your weakness and take advantage of it until you fail. Every player must be looked at individually, but being a top prospect and having a high walk rate is a really good place to start.