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BASEBALL ANALYTICS

Analyzing the relationship between power and plate discipline

Traditionally, it is thought that hitters with more power have a lack of plate discipline, swinging erratically at bad pitches. This report analyzes this stereotype.

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OVERVIEW 

This report uses data from the 2018 Major League Baseball season, for the top 150 hitters in the league. The data was compiled and pulled from Fangraphs. Fangraphs allows you to pick stats of your choice, and then compiles these stats into a csv file. 

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This report analyzes plate discipline as it relates to home runs and power-hitters. Multiple existing Sabermetric statistics are used and plotted in an attempt to show a correlation between plate-discipline and power. ​

 

The plate-discipline metrics used include Swing %, O-Swing%, Z-Swing%, Zone %, and F-Strike %. which will be explained in detail later in the report. 

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The definitions of the metrics used are defined below, as explained by Fangraphs. 

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Greater strikeout rates must be a result of two possibilities:

  1. A hitter erratically swinging at bad pitches

  2. A hitter being approached differently by the opposing pitcher

THE METRICS

O-Swing % - Swings at pitches outside of zone/pitches outside of zone

Z-Swing % - swings at pitches inside of zone/pitches inside of zone

Swing % - swings/pitches

Zone % - pitches in the strike zone/total pitches

F-Strike % - first pitch strikes/plate appearances

These metrics analyze a batter's discipline. They shed light on his ‘eye’ for pitches outside of the strike zone, as well as the pitcher’s approach to the hitter. For example, F-Strike % is used to reveal a pitcher’s aggressiveness towards a given hitter, by showing the amount of first pitches that are thrown in the strike zone. 

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This report analyzes plate discipline as it relates to home runs and power-hitters. Multiple existing Sabermetric statistics are used and plotted in an attempt to show a correlation between plate-discipline and power. ​

Finding Sabermetrics that analyze a hitter's 'batting eye,' as well as the way pitcher's approach them.

METHODOLOGY 

The data was compiled from Fangraphs through their custom table creator, which allows the user to pick relevant statistics they would like included in a csv file for the top 150 hitters in baseball. This CSV file was then put into a database and converted into a .sqlite3 file. 

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DataFrames were created for each sabermetric statistic listed above, juxtaposed with the Isolated Power for each player.  

 

The data pulled from the 2018 MLB season seems to point to the fact that although power hitters are more prone to higher strikeouts, it is not due to a lack of plate discipline. Rather, the data seems to suggest that the higher strikeout rate is correlated to pitcher’s approaching these power hitters with greater caution, and offering them fewer hittable pitches in the strike zone. 

THE CODE 

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ZONE%

The first query analyzed is Zone %, which tracks the percent of pitches in the strike zone that every hitter receives. Joe Mauer received the highest percentage of pitches in the strike zone, while only hitting 6 Homeruns. Salvador Perez received the least amount of pitches in the strike zone, and hit 27 Homeruns. 

F-STRIKE%

Next analyzed was F-Strike %, which calculates out of all first pitches a batter receives, how many of them were strikes. The batter that received the highest First Strike rate was Jose Altuve, with 67.8%, while hitting 13 homeruns. The batter that received the lowest first strike rate was Rhys Hoskins, with 52.4%, while hitting 34 homeruns. 

STRIKEOUTS

The next stat calculated was total strikeouts. This was juxtaposed with a batter’s total homeruns. Yoan Moncada had the most strikeouts in 2018, with 217. The batter with the least strikeouts was Andrelton Simmons, with 44. 

SWING%

The next stat analyzed is Swing %, which calculates how many swings a batter takes per pitch. Joe Mauer had the lowest swing rate at 35.3%, while Corey Dickerson had the highest swing rate at 59.3%. Mauer hit 6 homeruns, while Dickerson hit 13. 

O-SWING%

O-Swing% calculates the rate at which a batter swings at pitches outside the strike zone. A low o-Swing % is thought to correlate with a batter having a ‘good eye’ for the strike zone, while a high o-Swing % means the batter has little awareness of the strike zone, and can be categorized as a ‘free-swinger.’ Joey Votto had the lowest o-Swing %, at only 16.4. Salvador Perez had the highest o-Swing % at 48.4%. Votto hit 12 homeruns, while Perez hit 27 homeruns. 

Z-SWING%

The next stat calculated is z-Swing %, which tracks how many pitches a batter swings at inside of the zone. Joe Mauer had the lowest, at a rate of only 51%, while Freddie Freeman had a rate of 85.1%. Mauer hit 6 Homeruns and Freeman hit 23 homeruns. 

DISCUSSION

This report attempts to visit the age-old concept that power hitters in the MLB often have the worst plate discipline. They are often though to strike out more often, and be ‘free swingers,’ frequently swinging at pitches outside of the strike zone. However, this lack of plate discipline is also thought to translate into higher power and more homeruns. The purpose of this report is to see if this claim is true, and if it is necessary for hitters are truly sacrificing plate discipline for increased power. 

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It is not a surprise that players that hit more homeruns strike out much more often. There is an obvious positive correlation in the scatterplot between homeruns and strikeouts, suggesting that indeed power hitters do strikeout at higher rates than non-power ‘contact hitters.’ 

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When analyzing a batter’s plate discipline more thoroughly, however, there seems to be almost no correlation between a batter’s power and the percent of pitches they swing at inside the zone, outside the zone, or their total swing rate. So although they strikeout at higher rates, it does not seem to be due to a lack of plate discipline, as is often thought to be the case. This is an extremely interesting insight, as it suggests that the higher strikeout rate of power players must be coming from an alternative cause, and not due to the long-thought falsehood of this lack of plate discipline.  

Although the league’s best power hitters may not have any less plate discipline than the league average, it came to the surface that they were often pitched to very differently. There was an obvious correlation between a batter’s zone % and their homerun total, suggesting that opposing pitchers are much less likely to throw strikes in the zone to hitters with greater power. On the flip side, opposing pitchers are much more likely to throw pitches in the zone to batters with perceived less power. 

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Furthermore, there was a correlation between a batter’s power and the rate at which the first pitch of their at bats were strikes. Batter’s with more homeruns tended to have lower first strike rates, while batter’s with less power had higher first strike rates. This is undoubtedly due to the pitcher attempting to “pitch around” a batter with more power, while coming right after a batter with less power, as they pose less threat. 

Ultimately, a batter's 'lack of plate discipline'

is not directly related to their own tendencies

 

Rather, it should be attributed to pitchers approaching them more fiercely.

SUMMARY

The data pulled from the 2018 MLB season seems to point to the fact that although power hitters are more prone to higher strikeouts, it is not due to a lack of plate discipline. Rather, the data seems to suggest that the higher strikeout rate is correlated to pitcher’s approaching these power hitters with greater caution, and offering them fewer hittable pitches in the strike zone. 

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