Plate Discipline Definition
One of the fundamental keys to good hitting is to swing at the strikes and leave the balls alone. It’s hard to make solid contact on pitches out of the zone, so letting those pitches fly by is a valuable skill and that skill is referred to as plate discipline.
Plate discipline isn’t one stat but rather a collection of stats, each of which tells a slightly different story. Analyzing the various plate discipline stats for a given hitter can reveal strengths and weaknesses, highlight the batter’s game plan, and even reveal what kinds of pitchers may give him trouble.
The Concept of Plate Discipline
The concept behind plate discipline statistics is to take a closer look at what happens within each at-bat. Sure, you can learn something from the fact that the batter hit a home run or struckout in a given plate appearance, but that is results-based analysis. To dive deep, you need to analyze the process, which is where plate discipline stats become so important.
Plate discipline numbers look at how a player handles his at-bats, rather than just looking at the outcomes. What is his approach at the plate? Is he swinging at a lot of pitches, or being patient? How often is he swinging and missing?
There are countless questions that can be asked and answered here, depending on which specific plate discipline stat is being used.
Why is Plate Discipline Important?
Countless players over the years have been unable to stick around in the Major Leagues because they did not have the necessary plate discipline. For instance, a power hitter might be able to slug his way through the minors and earn a call up, but chasing too many pitches out of the zone will make for a short big league career, as the best pitchers can take advantage of such an aggressive approach.
What are the Plate Discipline Statistics?
We’d like to introduce a total of nine statistics which fit into the plate discipline category. These stats are listed below, along with a quick explanation.
Swinging Strike %
The frequency with which a batter swings and misses.
Outside the Zone Swing %
How often a player swings at pitches that are not strikes.
Inside the Zone Swing %
How often a player swings at pitches in the strike zone.
Swing %
How often a batter swings at all pitches combined.
First Pitch Strike %
Frequency of first pitch strikes thrown to a batter.
Inside the Zone Pitch %
How often pitches are thrown in the strike zone to a batter.
Outside the Zone Contact %
How often a batter makes contact on pitches outside the zone.
Inside the Zone Contact %
How often a batter makes contact on pitches inside the strike zone.
Contact %
Frequency of contact made per swing
While they all seem somewhat similar, each of these stats give us a different piece of the puzzle. Further, looking at several of these stats for the same player is a great way to put together a clear picture of his batting profile.
How is Plate Discipline Calculated?
The calculations for these stats are extremely simple, as long as you have the underlying data necessary to do the math. Of course, if you don’t want to do the math, the stats can be found already calculated on FanGraphs leaderboard pages.
- Swinging Strike % – Swing and miss / Total pitches faced
- Outside the Zone Swing % – Total swings on pitches outside the strike zone / Total pitches outside zone
- Inside the Zone Swing % – Total swings on pitches inside the strike zone / Total pitches inside zone
- Swing % – Total swings / Total pitches faced
- First Pitch Strike % – First pitch strikes / Plate appearances
- Inside the Zone Pitch % – Strikes / Total pitches faced
- Outside the Zone Contact % – Contact made outside strike zone / Swings on pitches outside the strike zone
- Inside the Zone Contact % – Contact made inside strike zone / Swings on pitches inside the strike zone
- Contact % – Pitches on which contact was made / Total number of swings
What is Good Plate Discipline?
Good plate discipline is hard to define. Sure, one player may excel in a given category, but what about all the other categories? It’s more useful to look at a player’s overall plate discipline profile than to just highlight the leaders in specific stats such as swinging strike % or contact %.
We are going to offer three different plate discipline profile examples in this section.
2018 Plate Discipline Statistics, Mike Trout, Alex Bregman, and Joe Mauer
| Stat | Mike Trout | Alex Bregman | Joe Mauer |
| O-Swing % | 20.7% | 20.0% | 21.1% |
| Z-Swing % | 60.8% | 60.5% | 51.0% |
| Swing % | 36.7% | 37.1% | 35.3% |
| O-Contact % | 69.2% | 79.1% | 72.3% |
| Z-Contact % | 88.8% | 92.8% | 94.0% |
| Contact % | 82.2% | 88.5% | 87.2% |
| Zone % | 40.1% | 42.3% | 47.6% |
| F-Strike % | 52.5% | 54.0% | 60.4% |
| SwStr % | 6.4% | 4.2% | 4.5% |
Mike Trout and Alex Bregman were two of the best hitters in the league in 2018. Joe Mauer, while long one of the best hitters in the league, was in the last year of his career and posted roughly league-average numbers. In some categories, like O-Swing %, all three are very similar. In other areas, however, such as Z-Swing % and F-Strike %, Trout and Bregman stand apart from Mauer.
What are the Problems with Plate Discipline?
There are a lot of variables involved in the collection of plate discipline statistics, so they should be viewed with the understanding that there is a margin of error involved. Called strikes are objective, as they are based on a split-second decision by the home plate umpire. Not all stats include this element of subjectivity, so that needs to be considered.