Passive Hitter Analysis
Which teams and hitters were most passive at the plate in 2023? Do passive hitters typically stay passive? Who could benefit the most from swinging more aggressively in 2024?
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There’s a lot of talk out there these days about swing decisions. From my perspective, this is a bit of a new frontier in baseball analysis. Ever since 2016, we have had precise data about the locations of every pitch thrown. The analyst community initially dug much more into other parts of the new data, like pitch velocity and movement, launch speed and angle, etc. But it seems now we’re moving into examining closely the locations of the pitches in terms of what hitters are doing.
So we hear a lot about how good each hitter is with his “swing decisions”. These metrics just give us an idea of which hitters are best at swinging at advantageous pitches and letting the disadvantageous ones go by.
I do think that we’ve gone too far, this offseason particularly. I’ve seen plenty of hitters being hyped up because they make very good swing decisions. The problem is that, if you can’t hit the ball well when you’re swinging at it, your swing decisions don’t matter at all.
Taylor Walls is fantastic at knowing what pitches to swing at. He swings at 43% of pitches overall, 66% of pitches in the zone, and just 18% of the pitches out of the zone. 80.3% of his swings in 2023 were at pitches in the strike zone, which was third-best in the league! Despite that, his contact rate was middling at 73% and his barrel rate (3.3%) and xwOBA (.273) were awful.
Conversely, Yainer Diaz was one of the worst hitters in the league, having just 58.7% of swings being at pitches in the zone, but he was quite effective at the plate. So we have deceptive numbers at both ends of the spectrum.
So we need more information than just swing decision stuff.
None of this is even the point of this post, however, but it’s a good thing to understand nonetheless.
The question I asked myself to inspire this was this:
Do passive hitters stay passive year over year?
The specific hitter that came to mind was Jack Suwinski. He did not swing very often last year (39% of the time vs. a league average of 47%). Because of that, he posted a strong 18% Chase% (league average = 28%). When he is swinging and making contact, his power is fantastic, and his contact rate isn’t horrific either at 70% (league average = 74%).
So in my mind, it would make some sense for him to come into 2024 with the idea that he’ll swing more aggressively. With his great power and non-awful contact abilities, more swings overall will turn into more swings at advantageous pitches which will lead to more home runs. Maybe that’s over-simplified, but that was the thinking.
My first question. Did passive swingers in 2022 stay passive in 2023?
Here’s my data file if you want to follow along or explore for yourself.
A general rule of thumb is that hitters at the extremes of any list one year will gravitate toward the center the next year. That’s simple regression to the mean. But with swing stuff, we don’t expect regression to the mean generally (meaning not at the extremes) because swinging is a conscious decision.
If we look at the lowest zone swing rates from 2022 and compare to 2023, we do see all of the top 10 increasing their zone swing rates in 2023, but none of them came up from the bottom to anywhere near the league average (67%).
So just looking at the extremes doesn’t do much good.
What I did next is group everybody into one of four groups based on their 2022 Z-Swing%
“Very low”: Below 25th percentile of z-swing
“Low”: Between the 25th percentile and the average
“High”: Between the average and the 75th percentile
“Very High”: Above the 75th percentile
Then I can average each group to see the group’s change in Z-Swing from 2022 to 2023.
Very Low Group = +0.6%
Low Group = +0.3%
High Group = -0.3%
Very High Group = -2.9%
If I look at it in terms of percentage change rather than raw points change (going from 35% to 40% is not the same as going from 85% to 90%. The first one is a 14% change and the second one is a 6% change):
Very Low Group = +1.1%
Low Group = +0.4%
High Group = -0.4%
Very High Group = -3.9%
Same results. The very high zone-swingers made much bigger changes than the very low group, the guys in the middle both moved toward the middle at the same rate.
That’s interesting! For our purposes though, it doesn’t seem to lend any credence to the idea that these passive swingers from 2023 will change much in 2024.
Let’s push forward on this. Another very important thing that we haven’t mentioned yet is how strongly correlated z-swing is with overall swing rates. We often praise hitters for their low chase rates not recognizing that they have a low swing rate just because they aren’t swinging at anything at all.
I looked at this in-depth last year.
So if we’re holding hitters up as positive or negative in how often they chase, we have put some controls in concerning how often they swing overall.
In our data file, for each 2022 and 2023, I took each hitter’s overall swing rate percentile and their zone-swing rate percentile and compared them.
The winner of this was Matt Thaiss.
Swing%: 46% (37th percentile)
Z-Swing: 72% (83rd percentile)
Pct Diff: 46% (83-37)
Here are the top names:
So it’s mostly a list of good hitters. Some exceptions are Thaiss, Belt, Bleday, Vargas, and Taylor. Those names generally struggle with making contact. How often you swing at what kind of pitches has nothing to say about how good you are at making contact, so we really want to consider that as well.
The bottom of the list:
There are a few good hitters here as well (Harris and Duvall), but in general terms, this is a list of unsuccessful hitters from 2023. I believe this does show a real problem for a hitter, they clearly struggled with pitch recognition - and that is a key part of being a successful hitter.
It seems to me that:
You can be a bad hitter even while making very good swing decisions
It’s hard to be a good hitter while making very bad swing decisions
Comparing those percentage differentials from 2022 to 2023 to see who most improved with their swing decisions:
It’s a little surprising to me to see so many veterans here. My hunch was that young players would be the ones most improving here, but that wasn’t the case generally. We do our boy Jack Suwinski here, and some other 2-3 improvers at the plate like Marsh, Murphy, Ozuna, Witt Jr., and Taveras.
But it’s still a mixed bag. Improvement on this front does not seem to correlate highly with improvement in your overall hitting production.
Picking Out Potential
What we’ve found here is less than useful. I think the main point of all of this swing stuff is that it’s much too simple by itself to be predictive in anything substantial.
So the names I pick out below aren’t strong recommendations, they are just theoretical.
What I’m curious about now is which hitters in 2023
Had low overall swing rates
Made good swing decisions
Had above-average zone contact rates
The idea here is to find hitters that swing at the right pitches, don’t whiff at them too much, and have room for growth in overall swing rates.
I chose
Z-Contact% > 84%
At least a 10 percentile positive difference between z-swing and swing
Overall swing% below 47%
We see Acuna Jr., so his ridiculous resume expands. He was amazing at knowing what pitches to swing at, one of the best in the league when making contact, and he was letting plenty of pitches in the zone go by.
Now maybe this shows something else very important - not all pitches in the zone are created equal. Letting a well-located strike go by can be just as beneficial as watching a ball. Some pitches you just can’t do anything with. This is harder to quantify, but it is what those advanced models are after.
I changed the criteria a bit and then filtered to some hitters that I know can impact the ball very well:
Five hitters here (sans Trout & Soler) who are very young and have already shown strong power abilities with good to great swing decisions.
Edouard Julien maybe should be the poster-boy for this post. He is fantastic when making contact, but very rarely swings the bat. His 44% Swing% certainly has room for growth, his zone-contact is at 79%, which isn’t great but it’s far from the worst in the league, and he seems to be good at pitch recognition with that 14.5 percentile differential.
I’m buying in on all of those young names, although full disclosure - I already was before this!
So this wasn’t my most useful post, I’ll admit. It was one of those posts where I do some investigation by myself and type my way through it, hoping that some useful advice would come out at the end. In this case, it didn’t really. But maybe it was interesting and informative regardless.