clock menu more-arrow no yes mobile

Filed under:

Astros Plate Discipline - Minor Leagues

The Crawfish Boxes examines the plate discipline of Astros prospects in the high minors


Yesterday, we published an article showing that the Astros' 2014 major league club boasted some of the top-disciplined batters at the plate.  Today, we use the same method to examine Astros prospects in the high minors.

The method involves using Z-Swing% and O-Swing% as a proxy for plate discipline by finding the rate at which the player identifies and swings at pitches inside and outside the strike zone.  While not perfect, this method is a simple way to represent which players are choosy about which pitches to take, and which players are not.

It's interesting to note that the Astros hired Dave Hudgens to be their batting coach at the major league level.  Presumably, his hitting philosophy matches that of manager A.J. Hinch, and that GM Jeff Luhnow wants to establish a consistent philosophy throughout the system.  As quoted in this article by, Hudgens said, "Hunt your pitch...We want to do damage in the middle of the plate...If he doesn't give you that pitch? We're walking to first base."

In plainer English, Hudgens' hitting philosophy is what this plate discipline proxy looks at - swing at pitches in the zone.  Note, there's the obvious caveat that we mentioned yesterday -- this estimation of plate discipline slightly penalizes players that lay off of pitches in the zone that are likely to result in a negative outcome, such as low-and-away, and slightly penalizes batters with the contact and running ability to get on base despite bad plate discipline, like Jose Altuve.  But by-and-large, it's an overview of which players are being selective.

Luckily for those of us confined to the cold dark reaches outside of the Astros' nerd cave, swing tendencies for batters are collected at most Triple-A and Double-A parks these days, and are published at  Using that data and the formula ([Strikes swung at]+[balls taken])/(No. of pitches seen), the crack researchers at The Crawfish Boxes are able present the following information for the 2014 OKC Redhawks and Corpus Christi Hooks.

AAA/AA Rank is where batters rank in "plate discipline" out of all players who saw 500 pitches at the level in 2014.  To ignore non-prospect journeyman with lots of experience who are just cluttering the data, we limited the sample to those players younger than age 25.


  • Interesting that the "Good Decision" percentages are by-and-large 10 points higher than those in the MLB.  One reasonable explanation is that this reflects the difficulty difference between the major leagues and the highest level of the minors.  Pitchers in the majors are so much better that batters really do have more difficulty identifying and/or adjusting in the majors than they do in the minor leagues.
  • At AAA, Robbie Grossman literally swung at zero pitches.  Well, perhaps "zero" is an exaggeration, but his 19th-percentile plate discipline has everything to do with the fact that he didn't swing very often.  He only offered at 18 balls outside the zone over his 199 plate appearances. Out of all players who saw fewer than 800 pitches, Grossman led the "strikes taken" column by a wide margin.
  • One would think that with a 1:10 balls swung to balls taken rate, Ronald Torreyes would have a higher walk percentage than 5%.  While the data isn't available, this suggests that he becomes a little more eager in two-strike counts.  It's a shame - with that sort of plate discipline, he should be able to do a bit more damage.  But with no power and little speed, it looks more like he just hits into too many weak outs to be a strong offensive player at the next level.
  • If Andrew Aplin had qualified for this list (he saw 472 pitches at AAA), he would have ranked first among Astros prospects with an 82.2% good decision rate.  This is odd, if you look at what he did in Double-A, below.  Small sample?  Swinging the bat more?  It's an oddity.  His "take-pitches" style of offense profiles similarly to Robbie Grossman, so 2015 should tell us if this is development or not.
  • Comparing Jonathan Villar's 76th percentile at AAA to his 53rd in MLB points to struggles adjusting to the difficultly of The Show, and maybe that he was pressing a bit to make an impression.  Hopefully next year in the majors he displays the sort of discipline he showed last season at Triple-A, where he had a 14% walk rate.
  • Jonathan Singleton's rank in both Triple-A and in the Majors is promising, and points to a correction in 2015.
  • One can't help wondering about Joe Sclafani.  A no-speed no-power batter cannot afford to have poor plate discipline.  On the other hand, there may be something missing from the equation.  How can a fellow with his plate discipline score have a 12% walk rate, a 12% strikeout rate and a 130 wRC+?
  • Does Domingo Santana's average plate discipline combined with his high whiff rate concern anybody?  Or are we still playing the, "he's very young" card?

And at Double-A, below.  Unfortunately, stats for the Eastern League are not available, so the ranks below represent those players who amassed 500+ pitches seen in the Texas and Southern Leagues only.


  • It feels like Telvin Nash has been in the Astros system forever.  But could it be that Nash is an actual major-league prospect?  Granted it's an understatement to call his strikeout rates alarming, but he walks a-plenty, has good strike zone judgement, and oh, that power.  He'll be an interesting one to follow.
  • Nolan Fontana and Andrew Aplin suffered from Grossman-ism - they don't swing at enough pitches in the zone, and that hurts their plate discipline score.  That might not stop them from being productive offensive players, but without power or speed to speak of, it could limit their ceilings.  Fontana has watched almost as many strikes sail through the zone as he has swung at them.
  • Again, we see Sclafani ranking low in plate discipline.  The discrepancy between Sclafani's effectiveness at AA and AAA may be due to his sky-high AAA BABIP.  Judging by his plate discipline and tools, his 2014 at AA is probably more representative of his median projected production level.
  • Preston Tucker - does this guy do anything poorly at the plate?  He's strongly above-average at every skill required to drive in runs.  No wonder the Astros seem to like him.
  • Brandon Meredith might be one of those older, unheralded guys who winds up having a surprisingly-successful major league career.  For his sake, we hope so.  If one can overlook his unpleasant career batting average, one sees that he is an on-base machine with a tolerable strikeout rate, intriguing power, and excellent plate discipline.
The research discussed in yesterday's article shows that a player's plate discipline varies little with time and experience once he reaches the Major Leagues.  However, the data isn't publicly available to show if a player can improve this skill earlier in his career while he is still in the minor leagues.  It is possible, for example, that something "clicked" for Andrew Aplin this season, resulting in him moving from a below-average disciplined hitter to an above-average one.  But either way, the information shown here is interesting and might be used in conjunction with scouting and on-field results to fill in some of the gaps in evaluating minor league hitters and projecting their major-league success.

Do any of your opinions change of the players shown above based on their plate discipline ranking?