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.

What Do Minor League Walk and Strikeout Rates Tell Us About Prospects? Triple-A Edition

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
389 of the 480 prospects in this dataset accumulated at least 150 plate appearances in Triple-A. 19% were successful, 20% were average and 61% were busts. This is close to the overall 21/21/58 trend for all prospects.

Walks

What Do Minor League Walk and Strikeout Rates Tell Us About Prospects? Single A Edition

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.

I have added a new feature, which includes 2007-2012 prospects. I followed exactly the same procedure as before in determining the very low to very high categories for current prospects or younger players. I listed only the top 10 or so for each category, instead of all players who fit that description.

History
Rookie and Low-A

Single-A
285 of the 480 prospects in this dataset accumulated at least 150 plate appearances in Single-A. This is quite a leap from the 111 number in Low-A, so the overall numbers here are a bit more interesting. 19% were successful, 20% were average and 61% were busts. This is much closer to the overall 21/21/58 trend for all prospects.

Walks

What Do Minor League Walk and Strikeout Rates Tell Us About Prospects? Rookie League and Low A Edition

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
I decided to only look at hitting prospects who appeared on a Baseball America list from 1990 to 2006, a total of 480 players. This provides an ample amount of time for us to know how the prospect fared in his career. Then, I took minor league plate appearance, walk and strikeout data from 1987 to 2011 from Baseball Prospectus. The Rookie league data may not be complete, but should be extremely close. Then I added Fangraphs WAR and other assorted Major League offensive metrics for each prospect.

I removed all minor league data after a player accumulated 100 Major League PAs, removing rehab and non-prospect years. Then I created level average metrics by year: BB/lvlBB*100 and SO/lvlSO*100. This doesn't account for the various leagues (International versus Pacific in AAA) but it's better than nothing. I calculated a weighted average for players who spent multiple years in the same level.

Next, I wanted to account for small sample sizes, so I only looked at players who accumulated more than 150 total plate appearances per level. Then I calculated a variance for each player from the average for qualified players at each level for both walk and strikeout rate: (BB/PA+ - average BB/PA+ for qualified players)/Standard deviation BB/PA+. Finally, I split players into categories of Very Low, Low, Average, High and Very High, based on this variance.