Insights About Hit By Pitch

“The coolest hit by pitch thing that I had, happened last year [2019]. I got hit 3 times in a game in AAA. That’s a ton. The next day I got called up to the big leagues. We were in San Francisco, I got hit 3 times again. So I had 8 at bats and got hit 6 times in two different leagues.” — Tim Locastro

Through 12 May, Tim Locastro had 22% of the Diamondback’s hit by pitch. The team had three additional leaders ( Carson Kelly 22%, Alex Young 17%, and Wyatt Mathisen 22%).

I tip my hat to Jack Sommers. One of his tables (4 true outcomes) inspired me to look further at the statistic hit by pitch (HBP).

As of 12 May, this season the Dodgers had the most HBP per game played. And which team is falling behind? For this season, and the last two seasons, the Rockies had the least HBP per game played. HBP must be significant for two reasons:

• The team with the highest odds of winning the World Series (24% as of 13 May per 538.com) had the most HBPs.
• The team with the fourth lowest odds of winning the World Series (<1%) has consistently had the least HBPs.

Let’s look at HBP for the Diamondbacks and for the average of all teams.

HBP for the Diamondbacks and the average of all teams.

The following graph shows yearly trends for hit by pitch.

Data from FanGraphs.

The graph shows that the rate of hit batters increased greatly in 2018 and continued to move higher. Nevertheless, in general the Diamondback starters had a lower rate of hit batters. The Diamondback relievers showed such high volatility that trends are obscured.

Comparison of the rate of hit batters and Wins Above Average (WAA) showed that in 2017, when the Dback pitchers (starters and relievers) had their highest WAAs of 11.5 and 1.5, their rates of hit batters were within 0.03% of their lowest from 2010 through 2021. In other words when the pitchers were remarkably great, their rates of hit batters were remarkably low. I’m not sure whether a causal link exists.

Pitches per PA did not increase enough to explain increased HBP trends.

From 2010 to 2020, pitches per PA increased 7.3%, while hit by pitch increased 50.6%. The following graph shows that pitches per PA did not change as much as HBPs.

Data from Baseball Reference.

Did lower control of pitch location explain increased HBP trend?

Let’s look at three trends to see whether this idea holds water.

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The first indication of reduced control of pitch location would be increased wild pitches. Let’s look at it. The following graph shows the trend for wild pitches.

Data from FanGraphs.

The Diamondbacks’ wild pitches fluctuated around the average for all teams; In 2020 they were equal at 1 wild pitch per 100 batters. This season through 13 May, the Diamondback pitches had extraordinarily few wild pitches. Will the rate of wild pitches increase to 1% later in the season?

The important observation is that the increase in wild pitches (12.5% from 2010 to 2020) was much less than the 50.6% increase in hit batters per plate appearance.

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The second indication of reduced control of pitch location would be increased pitches in wastage zone (so far from the strike zone that batters rarely swing). Let’s look at it. The following graph shows the percentage of pitches that crossed the plate in the wastage zone.

Data from Baseball Savant.

For the average of all teams, this graph shows from 2010 to 2021 that the percentage waste pitches stayed at the same general level, with a small drop in the middle years. For the Diamondbacks this graph shows from 2016 to 2019 that the percentage of waste pitches was higher, then fell dramatically in 2020 and 2021. It appears the Diamondback pitchers improved their pitch control in 2020 and 2021.

The important observation is that the percentage of waste pitches did not explain the increase in hit batters per plate appearance.

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The third possible indication of reduced control of pitch location would be increased walks. Let’s look at it. The following graph shows the trend for walks.

Data from Baseball Reference.

This graph shows that from 2010 to 2021 that the percentage walks hit a low point in 2014, and steadily rose after that. From low point to the peak in 2020, the percentage of walks increased 20.2% for the average of all teams.

The increase in walks (4.7% from 2010 to 2021) was much less than the 50.6% increase in hit batters per plate appearance. The important observation is that although the 20.2% increase from 2014 to 2020 is suggestive of less pitch control, the increase in wild pitches is the better indicator.

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A final explanation of the increase in hit batters would be an increased percent of pitches in the inner third of the plate. Let’s look at it.

For right handed batters, from 2010 to 2021, the percentage of pitches on the inner third of the plate (closest to the right handed batters) fell from 26.2% to 24.8%. No need to look at the graph.

The important observation is that for left handed batters, from 2010 to 2021, the percentage of pitches in the inner third of the plate (closest to the left handed batters) rose from 19.8% to 25.1 %. That was a 27.0% increase in percentage, suggesting an explanation for an increase in hit batters.

The following graph shows the increase in pitches in the inner third of the plate for left handed batters.

2021 games through 17 May. Data from Baseball Savant.

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Summary.

The rate of hit batters increased greatly in 2018 and continued to move higher. From 2010 to 2020, the rate of hit batters increased 50.6%.

Looking at that 50.6% increase: 12.5% can be explained by reduced pitch control (assuming wild pitches are the best indication), and 7.3% can be explained by increased pitches per PA. That leaves 30.8% unexplained increase in hit by pitches.

For left handed batters (unlike right handed batters), the remaining 30.8% increase in hit batters can be mostly explained by a 27% increase in pitches in the inner third of the plate.