AA Run Environments, Part II: Tennessee Walking

In Part I, we looked at rates of runs and homeruns in the various Double-A leagues along with some peculiarities of the Southern League. For Part II, I wanted to compare other aspects of play in an attempt to gauge the overall improvements in talent at AA.


I mentioned in this in the A+ post, but pitcher control shows significant improvement at AA, as measured by hit-by-pitch rate.

2011-13, 3-Year Averages
  League HBP%
A Midwest 1.26
  South Atlantic 1.40
A+ California 1.29
  Carolina 1.38
  Florida State 1.26
AA Eastern 1.17
  Southern 1.16
  Texas 1.23

Dmick mentioned that he would be interested in seeing data on wild pitches as another measure of control. I have tallied wild pitches and passed balls and am showing it here on a per baserunner basis, where baserunners are estimated as H+BB+HBP+ROE-HR. What we really want is WP+PB per pitches thrown with at least one runner on, but I think this is a decent estimate.

Wild Pitches + Passed Balls per 1000 Baseunners, 2011-2013
A League Rate
  Midwest 72
  South Atlantic 73
A+ California 62
  Carolina 64
  Florida State 54
AA Eastern 55
  Southern 51
  Texas 59

Interestingly, this measure does show significant improvement from the A to A+ levels, which wasn't evident in the HBP data. There is also a decrease from A+ to AA, though not as large as the A-A+ jump. 


For Defense, I’m again looking at unearned runs as a percentage of total runs.

2011-13, 3-Year Averages
  League UER%
A Midwest 16.7
  South Atlantic 15.3
A+ California 13.3
  Carolina 14.4
  Florida State 14.0
AA Eastern 12.3
  Southern 13.1
  Texas 11.9

Again there’s a pretty steady decline across levels. Defense steadily improves throughout the minors.

Minor League Walk Rates

While there is not a clear trend in walk rates in the minors, the Southern League routinely checks in with some of the highest in baseball. Its rankings among the twelve full-season leagues since 1998: 1st, 2nd, 5th, 2nd, 1st, 2nd, 3rd, 3rd, 4th, 1st, 1st, 1st, 2nd, 1st, 1st, 2nd.

2011-13, 3-Year Averages
  League BB%
A Midwest 8.7
  South Atlantic 8.7
A+ California 8.8
  Carolina 8.6
  Florida State 8.4
AA Eastern 8.7
  Southern 9.4
  Texas 8.3
AAA International 8.8
  Pacific Coast 9.0

I’m not sure what to attribute this to. In the absence of other information I would go with the umpires, though I can’t find any reports of them having egregiously small zones. 

My instinct is that playing in a league with higher than average walk rates is a good thing for Cub hitting prospects, who always seem to be singularly impatient. This is especially true if the BB’s are the result of a tighter strike zone. I don't know what the downside is for being rewarded more frequently for taking pitches. However, I do think it’s something to keep in mind when evaluating Cub prospects. For its part, the FSL seems to consistently be below average in the amount of walks issued, so prospects making the jump from Daytona to Tennessee may appear to be making progress in plate discipline whilst sporting an identical approach.

This year, Arismendy Alcantara and Javier Baez stand out as players whose walk rates I personally have been encouraged by during their time in the Southern League. I also seem to recall Brett Jackson having a pretty ridiculous walk rate one year at Tennessee. The context needs to be at least factored into those performances before attributing changes completely to an improved approach. Likewise, we should probably cut pitching prospects in the SL a little slack. Not that the Cubs have had many of those recently; Kyle Hendricks was unaffected.


The Double-A leagues are less distinct in their offensive environments than the Advanced-A Leagues, though the Texas League is the most hitter-friendly and the Southern League the least. Like most of the leagues we have surveyed, runs are fairly similar to the big leagues, with homerun rates varying considerably.

2011-2013, 3-Year Averages
League (HR/CON)% R/G
Eastern 2.8 4.4
Southern 2.6 4.3
Texas 3.2 4.5
MLB 3.6 4.3

The Southern League has a significant homerun split between the North and South divisions, and as a whole tends to feature higher walk rates than other minor leagues.

Next up is Triple-A.

Minor League Run Environments



Double-A (part I)


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