What Do Minor League Walk and Strikeout Rates Tell Us About Prospects? Recap

By Chris St. John


Introduction
A few months ago, I created a database that includes all of the prospect rankings from Baseball America, Keith Law and Kevin Goldstein. I didn’t have a direct purpose for it, I’m just the type of person who likes to accumulate as much data as possible. So it sat around on my computer until I found a good use for it. Well, thanks to fantasy baseball and Starling Marte’s horrible 3.8% walk rate in AA last season, I have. Marte is a possible target in my dynasty minor league draft and I wanted to see what other prospects had poor walk rates and how successful they were in their careers.

Method
In interest of saving digital space (and your scrolling finger), I will only post the full method on the Rookie and Low-A edition of this series.

History
Rookie and Low-A
Single-A
Advanced-A
Double-A
Triple-A

Bust Percentage
I calculated a percentage of players who were busts at each level for high and low walk rates and strikeout rates. Remember, the Rookie and Low-A levels had very small sample sizes, so their numbers don’t always follow the pattern. Looking at the data this way shows us where prospects have the most likely chance of failure.

I combined the Very Low/Low and Very High/High categories into one for simplicity’s sake.


A player is least likely to bust with a high walk rate, a probability that increases with level. Players with high strikeout rates early in their careers are more likely to bust than those who strike out a lot at higher levels. Not striking out is better than striking out, but it’s still no substitute for taking a walk. Not walking is about as bad as striking out a lot.

Productive Percentage
I also looked at where prospects became most productive. This is where they have the most likely chance of success.

The more a player walks at higher levels, the more likely he is to become a productive hitter. Players who don’t walk in the minor leagues are much less likely to succeed in the majors. Except in Double-A, players with either high or low strikeout rates are less likely to become productive than those with average rates.

Boom or Bust
This table shows the total percentage of productive and busted players at each category. The higher the percentage, the more likely a prospect in that category is a boom/bust player.

High strikeout players are the most boom/bust. Low strikeout players are most likely to become average MLB regulars, but not stars or scrubs.

2011 Triple-A
As we saw before, the best category a player can fall under to succeed is a high walk rate and an average strikeout rate in Triple-A. So let’s look at those players last year. I only looked at players with more than 150 plate appearances. I filtered the final results to show only players age 26 and under.

#FreeBrandonBelt
#FreeDomonicBrown

Not all of these players will get a chance, but I would like to see some of the younger players (Belt, Brown, Anderson) get constant big league playing time.

Conclusion
One final table (I promise this is it…for today):

“Most likely” is a bit of a misnomer, since a player is most likely to bust in pretty much every scenario. However, this table provides the most interesting descriptive term for each category.

And what about Starling Marte? A 12% success rate for prospects with low walk rates in Double-A was too much risk for me. I stayed away from him and took Oscar Taveras instead. You can read all about the rest of my draft at Steal of Home.

I plan on digging deeper into these data to find more trends in productive and busted players. I would also like to look into how players improve or decline as they advance levels and how that correlates with their success.

If you would like to know anything specific about the data, you can contact me in the comments section below or on Twitter @stealofhome.

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