Calling Balls and Strikes Against Catchers

This is a post that necessarily begins with an embarrassing story. Friday afternoon, I was doing some research into strike zones called against individual hitters, and full teams. I was comparing actual strikes against expected strikes, just as I’ve done with pitchers in the past. I didn’t know if I would find anything, but that was the whole purpose — it was statistical exploration. After some time, I gathered all my results in a spreadsheet, and then I remembered I already did this in October. Like the exact same thing, for this very website.

Memory jogged, I read the old post, and I read the old comments underneath the old post. Everything looked fine; I didn’t know what I was checking. All the results agreed, with the only difference being that this time I used a denominator of 1,000 called pitches instead of 1,000 general pitches. Hardly worth an updated post. But part of one comment did stand out to me, both because it was interesting, and because it meant I might not have to throw away all my data:

Dave S says:
October 19, 2012 at 10:39 pm
[...]
Do catchers get more calls than anyone?

It’s not immediately apparent why catchers might get a slightly different strike zone when they’re hitting than everyone else, but I figured there was enough there to pursue it, because it wouldn’t take a lot more work. If there was nothing, welp, that was only a few extra minutes. If there was something, hey look, there’s something! When catchers are in the field, there’s a catcher-umpire interaction, and there’s catcher familiarity with the strike zone. It makes some sense that there might be some sort of effect, then, that shows up when catchers are at the plate.

A quick refresher: it isn’t too challenging to gather pitch data, and strike data. I grabbed 2012 data from Baseball-Reference, since FanGraphs only has it for pitchers. I already had data for all players who batted at least 250 times. FanGraphs also has plate-discipline data, and from this data we can figure out how many pitches were thrown to each hitter in the strike zone, and how many swings each hitter took at pitches outside of the strike zone. From here, we can calculate expected strikes, and from there we can calculate the difference between expected strikes and actual strikes. Then we put it over a denominator of 1,000 called pitches, for purposes of standardization.

I separated catchers from non-catchers in the spreadsheet. For 2012, I had 33 catchers, totaling nearly 54,000 pitches, and 269 non-catchers, totaling more than 500,000 pitches. For all of the non-catchers, the average was a difference of -9 per 1,000 called pitches. That is, for non-catchers, per 1,000 called pitches, there were nine fewer actual strikes than expected strikes. The average isn’t zero because umpires are imperfect and the PITCHf/x strike zone is imperfect.

For all of the catchers, the average was a difference of -19 per 1,000 called pitches. That is, for catchers, per 1,000 called pitches, there were 19 fewer actual strikes than expected strikes. This separates them from the non-catchers by ten strikes per 1,000 called pitches. Looked at in another way, of the 33 catchers in the sample, 26 came out with a difference below -9. So, by this measure, in 2012, 26 were given more favorable strike zones than the average non-catcher.

When I looked at the initial list, I laughed when I saw Miguel Olivo getting one of the most favorable strike zones. I figured, he’s often behind in the count, when the zone shrinks, and also, if you’re an umpire, if Miguel Olivo doesn’t swing at a pitch, on some level you have to assume it was a ball. But this isn’t unique to Olivo. He’s just one guy in a much bigger sample.

The difference isn’t enormous — we’re talking one strike per 100 called pitches. It might not even be statistically significant. But there is at least some evidence now to suggest that catchers, overall, get more favorable strike zones when they’re hitting than non-catchers, overall. The reasons for this could be simple or complicated, and I won’t get into what they could be in here.

That’s because a whole lot more work could stand to be done on this before we say anything conclusive. We could, for one thing, get rid of the 250-PA minimum, since I just used that for convenience. We could look at more seasons than just 2012. We could perform a more direct and thorough PITCHf/x analysis, and we could try to control for count and batter size. What we don’t know, right now, is that umpires are kinder to catchers than non-catchers.

But they might be, as a general rule. Which would be interesting. There’s more yet to be done, but I’m satisfied with this starting point.




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Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.

28 Responses to “Calling Balls and Strikes Against Catchers”

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  1. thirteenthirteen says:

    Did you order it by other positions as well? It’s interesting that catchers receive a more favorable strike zone than other position players, but I’m just curious to know if there are any other positional relationships to strike zone.

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    • Did not do that, but might investigate that later.

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    • Cidron says:

      My kneejerk reaction is that aside from umpires calling the strikes, who else (as a batter) knows the strikezone of a given game’s umpire most? The catcher, that’s who. Not quite sure of the next step in that, but being aware of the strikezone of that given game’s umpire has to help in some way.

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      • thirteenthirteen says:

        You’re probably right – my first thought is that could potentially reveal something about the type of ballplayers that play different positions. Or maybe infielders vs. outfielders.

        Maybe it’d show nothing! I’m just curious.

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  2. Dave S says:

    Thanks Jeff!

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  3. Ian R. says:

    Olivo may only be one guy, but it’s possible he’s just the most obvious example of a trend among all catchers. In general, catchers are fairly terrible hitters, which means among other things that they’re more likely to end up behind in the count and thus deal with a shrunken strike zone. Of the 26 catchers who had fewer called strikes than expected, how many were weak hitters? Of the seven who didn’t, how many were good hitters?

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  4. Franco says:

    The kneejerk explanation is umpire bias in favor of catchers. I’ve never really noticed this in years of watching baseball so I’m actually not convinced of this. I have noticed umps being a little more forgiving of Hall of Fame type players on the back end of their careers. What’s the numbers on guys like Jeter or Chipper Jones?

    But it’s also a good theory that the catcher for example, knows that an ump isn’t calling the inner corner a strike so he doesn’t bother swinging at it himself. Other hitters probably have to get one PA in first before recognizing this.

    Either way, getting an extra missed call out of a 100 isn’t exactly a game changer.

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  5. James G says:

    I think this is pretty interesting (despite possibly being trivial). Have you tried sorting on different types of hitters. Say, free swingers vs. more patient hitters, tall hitters vs. short hitters, etc.

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  6. Thomas says:

    “It might not even be statistically significant.”
    Is it? This is pretty easy to check and one of the things that sometimes frustrates me about fangraphs. You guys really know you’re stats (a lot better than I do), but can a homey get an error bar or a p value every once in a while?
    Otherwise this is really cool stuff. I always love learning more about why we should have robo-umps.

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  7. Millsy says:

    Hey Jeff,

    I actually have an academic paper on this issue getting ready for journal submission (and posted a preliminary model a while back at my blog). I find that once we control for location and a host of other things, there does seem to be some effect. Shoot me an email if you have interest in reading the paper (and I am always happy to hear feedback).

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  8. Calvin says:

    Catchers are overwhelmingly righties- is there any handedness difference in bulk?

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  9. Scott says:

    Does this control for height? As a group, I would imagine catchers are significantly shorter.

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  10. Morgan says:

    Do the non-catchers include pitchers?

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  11. Stathead says:

    Is there a reason you said it “might not be statistically significant” but didn’t actually test for statistical significance?

    This isn’t just you. Fangraphs in general seems morally opposed to P-values and error bars (Oh god the error bars!).

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  12. maqman says:

    Error Bar? A bar for non-nerds?

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  13. maqman says:

    P-Values? Probably increase proportionately to the time spent in Error bars.

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  14. payroll says:

    I think I speak for everyone when I say, even when you might lack an explanation of “why,” these “I found somethings!” are still interesting and provoking content!

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  15. StatGeek says:

    “Statistical exploration”, aka “Datamining”?

    Tread very carefully. Conclusions may appear larger than they are in the proverbial rear view mirror.

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  16. AJ says:

    It makes sense to me for the most part. In my mind the main reason being that catchers are the only thing between the umpire and the unpleasant feeling of getting hit by a baseball travelling at 90+ mph. It might seem trivial, but I would give the guy who protects me (even with no men on in a lot of cases) a call or two. On top of that, in some cases I’d imagine it’s almost subconscious.

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    • siggian says:

      I think you are making the umpires think too much. The umpires should not be up there seeing the pitch and then think, “Well this guy has saved me from taking a pitch last inning, so I’ll do him a favour and call this close pitch a ball instead of a strike.”

      Instead, I think the catchers are exploiting where the umpire is calling balls and strikes. If this is the case, the advantage that the catchers are gaining should show up early in the game and then disappear as the batters gain more direct and indirect knowledge of what the umpire is calling.

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  17. g says:

    If the sample is large enough, try comparing catcher at-bats when they are catching that game versus catcher at-bats when they are playing another position that day.

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