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Which Braves hitters have been hurt by the de-juiced ball?

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Which Atlanta Braves hitters might be feeling like Lucy yanked away the proverbial football from them this season?

MLB: San Francisco Giants at Atlanta Braves Jason Getz-USA TODAY Sports

This is going to be kind of a weird post, because it sets out to answer a question that’s very difficult to answer. Before we get to why, let’s get some basics out of the way.

In June, Jeff Sullivan over at Fangraphs wrote an article noting that something paused the “home run spike” that had been “blamed,” in large part, on “juiced” baseballs. That’s a lot of quotes for one sentence. You can read that article, and a lot more. In particular, there’s an article by Jim Albert here that has a particularly instructive chart. We can talk about the reasons for the de-juicing ad nauseam. Here was Rob Arthur noting this at The Athletic (subscription required). And here’s an article from The Hardball Times featuring great stuff from David Kagan that pretty much just says, in addition to some really good other stuff that you should read, that MLB is effectively de-juicing the ball this season via mandated humidor use. Or, well, here’s Alex Chamberlain at Rotographs:

It’s substantially clear now — to me, at least — the ball has been de-juiced. (I don’t really care for semantics or the official prognosis, from MLB or otherwise; it waddles like a duck and it quacks like a duck.)

The point is, if you want to talk about physics and whether a juiced ball is good for the game/etc., great. That’s not really the point of this. This post starts with the premise that the ball is indeed “de-juiced” this year relative to past years. If that premise somehow doesn’t hold, you can leave this post to the dustbin of internet history, and that’s just fine. Anyway, onward.

We’ve discussed xwOBA before (in fact, earlier this week). The xwOBA calculation has to be calibrated in some manner: in order to calculate what wOBA on a given batted ball should be, you need to have some inventory of past results from which you draw what the wOBA on that batted ball (or similar batted balls) actually was. If you go to the Baseball Savant “Expected Stats” leaderboard (click here), you can see that for 2015 through 2017, xwOBA and wOBA largely matched. This makes sense because... xwOBA would be kind of a weird stat if they didn’t. The match wasn’t perfect (.005 underperformance of xwOBA in 2015, .002 overperformance of xwOBA in 2016, a deviation of less than .001 in 2017), but it was very close. But then, we get to this season, where league xwOBA is .327... and league wOBA is a measly .315. That’s quite a gap, in terms of averages.

(Also worth noting here that hitters have gotten better and better at making contact in the ways that should lead to better results. In 2015, league average xwOBA was .308. It increased to .316, .321, and then .327 this year. Yet the 2018 league wOBA is somewhere between where it was in 2015 and 2016 despite these gains — more evidence that we don’t need about something being off in baseball-land.)

The thing is, you don’t really need all of these fancy numbers to think about these things, you can just look at the Braves’ hitters over the past two years. That’s not a perfect measure, but it’s still suggestive.

  • Tyler Flowers had 12 homers in 370 PAs last year, and has just five in 225 PAs this year. The ISO has fallen from .164 to .112
  • Kurt Suzuki has 10 fewer homers in 12 more PAs this year. His insane .254 ISO from last year has fallen to .163.
  • Freddie Freeman has about 60 more PAs and eight fewer homers. He’s lost .076 points of ISO.

You do have some guys counteracting this trend. Nick Markakis has been straight better this year, and that includes more homers. Ozzie Albies had a homer surge earlier this season. Dansby Swanson is having an offensive bounceback that has included more homers; Johan Camargo replaced a BABIP-success-reliant profile last year with a more resilient and power-focused one this year. Ender Inciarte has essentially the same ISO as he did last year (.106 to .107). So, it’s not cut-and-dry, which gets into why this question is so tough to answer.

As you’re probably aware, you can’t answer this question by taking a player’s wOBA and comparing it to his xwOBA and going, “See, he’s being hurt by the de-juiced ball!” Lots of players don’t match their xwOBAs exactly over the course of a season — that’s what random variation, and baseball as a whole, is all about, and why we use xwOBA in the first place. (If they always matched, we wouldn’t need xwOBA.) If a player is underperforming his xwOBA, that could be because, on average, everyone is underperforming their xwOBA this year. Or, it could be because the player has gotten unlucky in terms of where fielders just happened to be. Think about someone like Tyler Flowers: he has a .313 wOBA this season but a .369 xwOBA. Has he been hurt by the de-juiced ball? Probably! But is that entire 0.056-point gap the result of the ball changing? Unlikely! It’s complicated

Given the data available, it’s difficult if not impossible to truly answer which Braves hitters have been hurt by the de-juiced ball. It’s tempting to basically reconstruct xwOBA at a granular level — see what combination of exit velocity and launch angle yielded which wOBAs in past years, and compare them to what’s happening this year. But the problem is that even this approach is fraught, not to mention incredibly time-consuming (and the fact that Daren Willman and company already did this, since that’s literally what xwOBA already is): even if you did this, you’d have no way of knowing where fielders were positioned in any given play unless you incorporated that as an extra data point, and thus couldn’t say anything just about the effect of the changed baseball on hitter outcomes.

Anyway, I don’t mean to make you read 1,000 words about why this question can’t be answered. I just want to warn you that the below is some combination of speculative and unsatisfying. Hopefully you find it interesting anyway.

Which batted balls are being affected?

To try to make this a manageable task, I decided to look specifically at launch angle. There’s probably another variant of this analysis that does the same thing for exit velocity instead, but I hope you’ll agree that intuitively, changes in the baseball are more likely to affect the subset of “balls hit at certain angles” than the subset of “balls hit at certain velocities.” The real answer is that the balls most affected are at some nexus of angle and velocity, but then we’re back to re-constructing xwOBA again.

I took every “band” of launch angle, and compared the gap between wOBA and xwOBA in 2015-2017 versus the same gap in 2018. I initially started with individual launch angles rounded to the nearest degree, but these data were very choppy. Using wide buckets of five-plus degrees of launch angles, meanwhile, was too aggregated to be of great interest. Instead, I settled on basically a series of rolling “bands,” where each band is consists of a given degree, with two degrees of leeway on either side. While I don’t need to replicate the whole table of every possible such band because it’s not very interesting, the basic idea is that you start seeing a divergence in wOBA-xwOBA “gaps” starting at 15 degrees (i.e., 13 to 17 degrees). This intensifies as you get to higher and higher launch angles until around 30 degrees, and then recedes until around 43 degrees (i.e., 41 to 45 degrees), at which point there’s basically no difference between 2015-2017 and 2018. This hopefully makes intuitive sense: if there’s something difference about the aerodynamics of the baseball, it’s going to matter when the baseball is airborne for a while and traveling at a trajectory that gets it further and further away from the plate. Balls hit at launch angles over 40 degrees are basically pop-ups that are easily caught, and altering the trajectory of a pop-up doesn’t really change how easy it is to catch. You’ve made it 1,360 words now, here’s a visual or two.

So, the conclusions here probably aren’t too complex. The more a hitter has hit struck balls between a launch angle of 13ish to 44ish degrees, the more the de-juiced ball has probably affected him. The most severe effects are potentially reserved for hitters with a tendency to strike balls at angles between 26 and 33 degrees. So, what does that say about Braves hitters this year?

This is, admittedly, a very rough measure. You can see that as a whole, the Braves have had all sorts of results on balls hit with a launch angle of 13 to 44 degrees. Some have gotten lucky: given that the league average 2018 xwOBA underperformance is 0.042 for these batted balls, only Flowers, Ronald Acuña Jr., and the kinda-sorta-departed Ryan Flaherty have really “underperformed.” That doesn’t mean, of course, that the other players haven’t been harmed by the de-juiced ball. It just means that other things may have made up for it. But, in terms of who’s the most likely to have been harmed, there are some fairly obvious candidates.

Flowers, Acuña, and Freeman have hit over 40 percent of their balls in play (and homers) at these, shall we say, “neutered” launch angles. When you add walks and strikeouts into the mix, the team leaders become Freeman, Nick Markakis, and Kurt Suzuki. However you slice it, Flowers probably has a legitimate complaint that MLB pulled the rug out from under his approach, as he increased his fly ball rate this year (launch angle gain of over two degrees on average relative to 2017) only to see his HR/FB rate fall by about a third. Acuña appearing at the top of this table raises a wondrous question: can you imagine him with the juiced ball, as opposed to the de-juiced one? Terrifying... for the rest of the league (maybe).

Freeman and Markakis could have legitimate complaints, but it may be hard for them to gripe too much. We can’t really know just how much the de-juiced ball has hurt them, but it’s hurt others elevating the ball more. Freeman is actually underperforming xwOBA by a fair bit this year, but a lot of that has to do with the shift; Markakis is underperforming xwOBA on paper, but doing so to an extent less than the league. Still, given that Freeman is currently on pace to post his lowest seasonal ISO since emerging as a Mecha-Godzilla slash MVP candidate in 2016, one wonders whether the change in the ball has had something to do with his altered results. More notably, though, Freeman has (consciously or not) changed his launch angle back to where it was prior to 2016. It’s not clear whether this was incidental to the change in the baseball, or a deliberate attempt to boost his batting line via line drives in the instance that Freeman feels he can no longer hit for prodigious power given the lack of carry on batted baseballs in 2018.

Kurt Suzuki is probably the most surprising name on the table above, in terms of his position. Suzuki’s remarkable 2017 season came out of nowhere, and it’s tempting to want to state that given his “pull fly balls duh” season last year, that the change in the baseball has undone what made him so successful. Yet, I’m not sure that’s the case. Not only is Suzuki not really suffering on balls with the “neutered” launch angle, but his barrel rate has fallen prodigiously despite exit velocity, launch angle, and hard-hit rates that are similar to last year. That suggests that rather than a change in the baseball (which could show up as worse results on a similar barrel rate), Suzuki’s downturn may have more to do with a weirder, suboptimal batted ball mix, such as one where hard-hit balls are being grounded rather than hit in the air, while weaker balls are the ones going airborne. Indeed, something like that is probably the case: Suzuki has gained about 1 mph of exit velocity on grounders this year relative to last year, but lost about the same on fly balls, and has lost over 1 mph on line drives. Combine that with a profile that’s hit a lot fewer flies this year in favor of liners (see side-by-side images below), and the situation clarifies itself. It seems like Suzuki should have been hurt by the change in the baseball, but I think the story is different. Of course, we don’t know if he de-emphasized flies because of a change in the baseball — that possibility only complicates the situation.

(For whatever reason, these charts don’t show the homers as red lines. But, last year, Suzuki’s homers were all hit between 21 and 36 degrees, with about half coming between 24 and 27 degrees. This year, the range has expanded to 23 to 42 degrees, with only a third in the 24 to 27 degree range, and no cluster anywhere, as he’s basically hit a few in the low 20s, high 20s, high 30s, and low 40s each. The point, as highlighted by the red circle, is that Suzuki may not really be hitting quite enough balls to really get the de-juiced baseball to stick in his craw.)

We can repeat this same analysis for the more targeted range of 26 to 33 degrees, and see what shakes out there.

Results here are interesting, but a little different. Acuña and Flowers are still some of the “most potentially harmed,” batters but now joined by Suzuki. While Acuña and Freeman hit the most balls at this “very neutered” angle, Freeman hasn’t actually suffered at all. League average 2018 underperformance for this bucket of launch angles is -0.058; Freeman has actually outperformed his xwOBA on these types of batted balls by more than that deficit. Acuña, though... we can’t say much, but I will say it would have been fun to see him mash with the ball all juiced up. This just further makes that point.

If you did want to make the case that Suzuki’s been harmed by changes in the ball, this table is as good as any, I guess. It’s still somewhat iffy because he really hasn’t hit that many balls at these angles, but he’s been brutalized on them results-wise, underperforming his xwOBA in a manner behind only Flowers and Acuña.

So, there you have it. It’s hard to be certain about any counterfactual, including ones about what would have happened had the baseball not been de-juiced in 2018. We’d possibly see much better results from Tyler Flowers, and even more ridiculously egregious numbers from Ronald Acuña. Maybe Kurt Suzuki’s power stroke would have been better, and perhaps Freddie Freeman would not have resulted to trying to spray line drives over the infield again. As for the other guys, aside from perhaps Nick Markakis — they may have been affected, but their results have been more than compensated for by sheer random variation.