The K Zone: Why strikeouts affect pitchers more than hitters

(Kathy Willens / AP)

by Patrick Barron

Ever wonder why strikeouts are more important for pitchers than for hitters?

Strikeouts are one of the most commonly examined stats when baseball analysts evaluate a player. Although strikeouts contribute to the benefit of pitchers and the detriment of hitters, the extent to which they affect each is arguably lopsided. We see this all the time: high strikeout players can end up earning high salaries, while a pitcher who strikes out less than 8 batters per 9 innings often struggles to obtain a huge contract (even if their ERA is low).  Much of this is due to the fact that a hitter has more consistency in and control over their individual batted ball statistics than pitchers do against opposing hitters. To show how strikeouts benefit pitchers I compared innings-qualified pitchers who this past year had opposing BABIP’s (batting average for balls in play) between .271 and .290:

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The players on the list with the lowest fWAR (Wins Above Replacement per fangraphs.com) were Ty Blach, R.A. Dickey, Jason Vargas, and Julio Teheran. All of these pitchers struck out fewer than 8 players per inning. Others with low strikeout rates include Michael Fulmer, who had the second-lowest HR/9 and HR/FB and had induced groundballs from about half the batters he faced, as well as Alex Cobb and Jhoulys Chacin who were more successful in inducing groundballs. The xFIP of the latter two both suggest they performed better than they actually are. Pitchers with the highest strikeouts include Luis Severino, Stephen Strasburg, Yu Darvish, Zach Greinke, Carlos Martinez, and Justin Verlander, who are all in the top 7 in fWAR among the 16 pitchers in the group. Martinez and Darvish did give up the most HR/FB of those six which is why they have the lowest WAR of the high strikeout group.

Pitchers, for the most part, must rely on striking out hitters to be successful. Yet even then a pitcher with a lower strikeout rate can have a successful career. This happens when a pitcher is able to consistency induce groundballs. This exception to the rule is fascinating when trying to understand how teams look at pitchers. Since there are pitchers that build a career off inducing ground balls, how is fWAR able to account for it? The answer to this is not very well. Shown below is the formula for how fangraphs.com calculates Wins Above Replacement.

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The main takeaway from this is that FanGraphs calculates WAR mostly based on Fielding Independent Pitching (FIP) which is a pitcher’s ERA that is calculated only using strikeouts, walks, and home runs. This does not account for being able to induce ground balls.

However, analyzing groundball pitchers gets more complicated. First of all, if you are the general manager of a team and you are thinking of signing a pitcher who is a ground ball pitcher, you need to have a strong infield to keep the pitcher’s opposing BABIP low. Analyzing groundball pitchers who are relievers is even more difficult since there is less of a sample size to show that they can consistently induce ground balls. This is why most teams look for relievers that rely on strikeouts, even those who may have had a higher ERA in the past, to join their team since there is a better chance that they perform better. Thus, while some starters who are able to produce groundballs consistently are still able to get good contracts, it is less common for relievers who have the same trait to do so. This illuminates the value of the strikeout among pitchers.

Hitters can often offset their high strikeout rates by making harder contact. Players can strikeout at a rate approaching a third of their at-bats, yet still finish high in WAR and wRC+ (which is weighted runs created plus and evaluates a player’s overall offense independent of park factors). For this, I compared AB-qualified players who led the league in strikeout percentage.

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Since wRC+ is a scaled metric that places the league average offensive production level at 100, it’s a great tool for comparing players. Only 5 of the top 16 in strikeout percentage produced below average offensive production this year (<100wRC+), and Trevor Story and Tim Anderson were the only players below 90 wRC+. The player who had the fourth highest strikeout rate, Aaron Judge, was rookie of the year this year. He also led the league in fWAR and was second in wRC+ overall. Now when looking at these players’ BABIP, only 4 players scored lower than .300. Only Tim Anderson and Byron Buxton, who both were below average hitters, hit fewer than 20 HRs and only 5 players hit fewer than 30. From these players only Tim Beckham. who had the highest BABIP of the 5, contributed above average offense. Also, only 6 of these players walked less than 10% of the time.

However, that seems a bit odd. Even if strikeouts are not the most important hindrance to batters, players with high K% should include some duds. Us baseball fans often find ourselves moaning in despair when that one batter who seems to strike out every time steps up to the plate. So let’s look at the 2017 leaders in K% who had more than 200 plate appearances.

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Now that’s more like it. Even here 5 of the top 16 strikeout-prone hitters were above average. However, a lot of these players had lower BABIP’s and BB%. Only 6 of these players slugged more than .450, yet this group contains 4 out of the 5 above average hitters. The fifth above-average hitter, Yoan Moncada, has the second highest BB% to Joey Gallo.

In conclusion, the data seems to support conventional attitudes concerning how strikeout rate affects pitchers and hitters. This is because pitchers have less consistency in terms of the contact their opposing hitters produce than the hitters themselves do. Hitters can offset their strikeouts with hard contact and by producing walks. Both of these actions seem to be reproduced more consistently than pitchers are able to produce ground balls or weak contact. Therefore, when deciding who to add to your fantasy baseball team, look for pitchers who strike out a lot of hitters. Yet if you can get Aaron Judge, absolutely get him.



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