For those who’ve learn any of my articles of late, you’d know that I’m at the moment fixated on plate self-discipline. My piece on Jarred Kelenic sparked an article on take value and hitter approach. After that, a discovery that Darin Ruf is succeeding with one of many lowest swing charges in baseball regardless of not having phenomenal plate self-discipline on the floor impressed analysis into zone-swing differential and what it might inform us a couple of hitter.
Below the plate self-discipline part of participant pages and on our leaderboards, we record each O-Swing% and Z-Swing%. On a handful of events, although, writers right here have used zone-swing differential. Chet Gutwein outlined this stat as D-Swing% in his piece about the NL West, and Justin Choi wrote about it in an article on the Blue Jays’ aggressiveness in early counts. In my most up-to-date piece on Ruf, I cited zone-swing differential to conclude that whereas his total swing fee is low, his self-discipline won’t really be that good, as he’s nonetheless swinging at a good quantity of pitches outdoors the zone, which you’ll see once you have a look at his below-average D-Swing fee.
The thought behind D-Swing% is easy: Hitters must be higher after they swing at strikes and take balls. This isn’t the one option to succeed on the plate, however you’d assume that higher hitters would have larger D-Swing charges on common. There have been a pair feedback about D-Swing fee on my Ruf piece, and that impressed me to look into it additional. Is that this a stat that tells us extra about hitters than what we have already got with the standalone O-Swing% and Z-Swing% stats?
This actual query was really explored on the FanGraphs community blog again in 2017, the place consumer Dominikk85 broke hitters into top- and bottom-30 teams by wRC+, ISO, OBP, and BABIP to see if O-Swing%, Z-Swing%, or what they known as Z-O-Swing% had the most important affect in explaining the distinction between the teams. They discovered that being extra aggressive within the strike zone “helps the ability however appears to barely harm the OBP,” however total, they noticed a bonus in utilizing D-Swing% over the person parts.
I ran the same research, however I wished to manage for extra variables — zone fee and phone fee — to isolate the impact of D-Swing%, as many plate self-discipline metrics are interrelated. Chances are you’ll swing much less at pitches within the strike zone if you’re seeing extra pitches outdoors, or you could select to swing at pitches within the strike zone with which you can also make contact (ideally laborious), which can decrease your Z-Swing% however elevate your Z-Contact%. With out not less than making an attempt to regulate for a few of these variables, we could also be lacking out on aware hitter tendencies that could be extra the results of the pitches that they’re seeing reasonably than their inherent swing selections.
That doesn’t make this methodology inherently higher, although. Whereas the relationships do enhance when adjusting for these components, we could also be capturing the connection between zone fee and, say, stroll fee, reasonably than precisely what we’re searching for; this might be an instance of overfitting. For full transparency, I’ll additionally present the non-adjusted figures to keep away from this. Adjusting could also be higher, however there could also be some essential insights to be gleaned from the uncooked relationships themselves. For all fashions, I simply used a linear relationship of 2021 hitters with not less than 250 plate appearances.
First, since D-Swing% is theoretically a plate self-discipline metric, we should always consider the way it pertains to top-line strikeout and stroll numbers so we will see how the metric performs relative to O-Swing% and Z-Swing% in explaining strikeout fee, stroll fee, and walk-to-strikeout ratio for hitters inside our pattern. “Managed R-squared” refers back to the r-squared worth after adjusting for zone fee and phone fee.
First, right here’s strikeout fee:
As you may see, all three of those swing metrics don’t correlate nicely to strikeout fee on their very own; they have to be contextualized with zone fee and phone fee to higher clarify the variations. This does recommend, although, that strikeout fee is much less depending on a hitter’s swing selections as it’s on how usually they see pitches within the zone and make contact when swinging, which is smart. In any other case, between the three swing decision-metrics, there’s not a ton of distinction within the effectiveness of explaining strikeout fee for hitters.
That’s not the case with stroll fee:
O-Swing% reigns supreme, and that additionally is smart: Hitters who swing much less steadily at pitches outdoors the strike zone will stroll extra. It additionally is smart that Z-Swing%, and consequently D-Swing%, isn’t as helpful in explaining stroll fee. It doesn’t matter what you do in your pitches contained in the zone; in case you don’t swing, these will usually be referred to as strikes, and in case you do, these pitches may very well be put in play, fouled off, or whiffed at. However in case you don’t put the ball in play, you’ll find your self in a worse rely (apart from fouls in two-strike counts) than you have been beforehand, which does clarify the slight destructive relationship between Z-Swing% and stroll fee; the affiliation is fairly muted in any other case.
If you put all of it collectively and think about walk-to-strikeout ratio, we as soon as once more discover O-Swing% as the perfect metric for a lot of these self-discipline numbers:
The ability of O-Swing% is why individuals like to cite chase fee for hitters. It’s true that hitters who swing at fewer pitches outdoors the strike zone will stroll extra, and strolling is among the finest issues a hitter can do. With a lot potential variability when placing a ball in play, a stroll is among the most constantly good outcomes for a batter after they’re on the plate. Barry Bonds hit a ton of homers, however it was his absurd stroll charges (due to pitchers being afraid of him) that allowed for constantly nice efficiency. If you get on base greater than 60% of the time, it’s not possible to be a nasty hitter. That’s why chase fee, and the way it pertains to stroll fee, turns into actually essential.
High quality of Contact
However chase fee isn’t the be-all, end-all for hitters. As I discovered in my article on Kelenic, a hitter’s manufacturing is finest modeled by how a lot success they’ve when swinging, and the highest hitters in baseball differentiate themselves by doing lots of harm on their swings. Can a metric like D-Swing% clarify precisely how a lot harm a hitter does when swinging, which may doubtlessly clarify extra a couple of hitter’s manufacturing total?
To search out out, I thought of two high quality of contact metrics, ISO and xwOBA on contact (aka xwOBAcon). There’s not too large of a distinction between the 2: ISO is production-based, and xwOBAcon captures the underlying exit velocity and launch angle knowledge. There’s unsurprisingly a powerful relationship between the 2, however I used each to see if we could be lacking one thing within the top-line energy numbers that xwOBAcon would account for.
First, listed here are the relationships with ISO:
There’s no inherent relationship between O-Swing% and ISO, however after adjusting for each zone fee and phone fee, the previous turns into a statistically important predictor of the latter, with larger charges of chasing related to decreased ISOs. What’s attention-grabbing right here, although, is that adjusting for zone fee and phone fee doesn’t assist the connection between Z-Swing% and ISO as a lot. Of the three, D-Swing% is essentially the most helpful metric in explaining high quality of contact after adjusting for zone and phone charges.
That additionally holds for xwOBAcon:
Once we use the underlying knowledge, all three metrics carry out higher. Once more, D-Swing% seems to be like the perfect metric to make use of after adjusting for zone and phone charges, however it doesn’t stand out as that significantly better than the opposite two on the entire.
Total Hitter Outcomes
How can we generalize this? Can we extrapolate past self-discipline and high quality of contact alone to reply the unique query? Do higher hitters have a better zone-swing differential?
The reply could be sure. Think about the connection between D-Swing% and wOBA. The previous explains 16.2% of the variation within the latter with no changes, performing significantly better at explaining hitter manufacturing than O-Swing% and Z-Swing% alone. All three metrics do carry out higher after adjusting, however once more, the mannequin utilizing D-Swing% has the strongest affiliation. And it does seem that hitters who’ve larger zone-swing differentials carry out higher:
The identical holds true when hitter xwOBA, although it must be famous that O-Swing% is simply nearly as good as D-Swing% after making the zone and phone changes:
However whereas it looks as if D-Swing% could also be useful as a catch-all swing-decision metric to explain hitter efficiency, it doesn’t blow current O- and Z-Swing charges out of the water.
With that in thoughts, it’s fascinating evaluating O-Swing% to Z-Swing%. We will see that avoiding swings outdoors of the strike zone seems to be rather more essential than all the time swinging when within the zone. That is in keeping with what I discovered when researching Kelenic: If the perfect hitters in baseball do essentially the most harm when swinging, they higher swing at pitches not solely within the strike zone, but in addition in their very own private wheelhouse. Avoiding chases is much more essential than all the time swinging when the ball is within the zone.
As for the usefulness of D-Swing% alone, extra analysis must be finished to see if it’s stickier year-to-year than the opposite swing metrics and if it does a greater job at predicting future manufacturing reasonably than simply associating with in-season marks. So long as my fixation on plate self-discipline doesn’t wane (why wouldn’t it?), this could be one thing to return again to within the offseason. For now, although, it does seem that this metric might have some standalone worth relative to those who are already revealed. However the conclusion is easy: Hitters ought to all the time swing at fewer balls. Whether or not they need to swing at extra strikes is dependent upon the kind of participant that they’re, and in addition on how pitchers method them.