Sonny Gray Rides Foucault’s Pendulum

Now back from the IL, which direction will Sonny Gray's momentum swing?

Foucault’s Pendulum sounds a lot fancier than it looks. You’ve probably seen one before: It’s a big pendulum that swings around non-stop and, thanks to some fancy math from 19th century physicist Léon Foucault, it was used to prove that the earth is in fact rotating on an axis. Someone call Kyrie Irving!

Foucault’s Pendulum is also a great metaphor for baseball. Baseball is a game of averages, and of course, averages aren’t built by simply being average all the time. Some aspects of a player’s performance swing one way, then they swing another. Metrics move from one extreme to another, and in any given year, a player’s status can depend on just how far they can ride the pendulum in any given direction.

Sonny Gray has seen more than his share of pendulum swings over the course of his career, which is perhaps why he finds himself the subject of a deep dive for the umpteenth time in recent memory. Over four-plus years in Oakland, he went from nascent ace to enigmatic underperformer, rebounding just in time to be traded to a contending Yankees team, where he almost instantly floundered before finding his footing in Cincinnati after a January 2019 trade.

Gray’s up-and-down nature isn’t anything new, and just a few weeks ago here, Lucas Zenobi chronicled the differences between Bronx Sonny and Skyline Chili Sonny. And indeed, things have been mostly sunny for Sonny since arriving in the Ohio Valley, consistently dominating in a way he’s rarely been able to consistently:

But if you’ve been paying attention in recent weeks, you’ll also notice that line creeping upwards on the far right of the chart. In particular, it’s been a disastrous September for the right-hander, who will shortly be activated from his IL placement immediately following starts in which he failed to get out of the 1st and 4th innings, respectively. Along the way, he gave up 11 hits and 11 earned runs, walking six while striking out just five. Ugly!

One or two bad starts is rarely a cause for concern on its own, especially when injuries are involved, and especially when injuries are involved in this dystopian campaign-that-should-not-be. However, Gray has been skating on thin ice for more than just two starts. Way back in January, Michael Ajeto noted on this site that Gray’s typically good breaking balls were getting hit a lot harder than the results indicated. Ultimately, he concluded, “his slider and curveball are nearly certain to show some regression next year, which means that if no changes are made, Gray is much more likely to look average or above-average than elite.”

Early in this season, it looked as though those fears might have been a touch overblown. Gray came out of the gates scorching hot, setting team records and leading the league in strikeouts through his first five starts:

Sonny Gray Through 5 Starts

(Source: FanGraphs; Baseball Savant)

Those are great results! Whether he technically overperformed in 2019 or not, it didn’t seem to matter early on. Just about every surface-level number screamed bona fide ace. Alas, as Michael put it to me, unwittingly inspiring this article’s guiding metaphor, “when the pendulum swings to, it shall also swing fro.” This particular turn of the pendulum took Gray farther than he ever had before, and rent was bound to come due in some form sooner or later. Gray didn’t begin to fully unwind until his last two starts, but more warning signs have been present since mid-August. Let’s tack on his last four starts to that chart and see what things look like:

Sonny Gray First 5 and Last 4 Starts

(Source: FanGraphs; Baseball Savant)

Those are … less great results. So what’s going on? The short answer is that his breaking balls are finally failing him, in a few different. Let’s back up a second and take it back to the critical chart in Michael’s piece that showed us exactly where Gray was catching breaks:


Okay, Gray was getting a bit lucky on breaking balls. On the other hand, he’s also been generally adept at outperforming peripherals over the course of his career. Having taken the strikeouts to another level last year, I initially thought that Gray had a better chance to stick as a legit ace than Michael was giving him credit for. The question at hand here isn’t whether Gray is actually good — we certainly know that much already — it’s whether he can continue to be as good as he was last year. The best pitchers in the game often outpitch their peripherals and expected stats because, well, that’s part of why they’re the best. It can be incredibly difficult to distinguish what’s luck and what isn’t, and that’s the question we’ve been asking about Gray for checks notes four articles running!

After having dug a little deeper, I’m afraid to say that I’ve grown to share Michael’s conclusion that true-ace Sonny is not much of a reasonable expectation going forward. Lest you think I’m overreacting to a couple bad starts in which he’s clearly been tired, injured, or some combination thereof, it turns out Gray was still walking an increasingly narrow tightrope, even as he dominated early this season. Let’s update that chart of expected stats on contact to reflect his 2020 results, first in his ace-worthy stretch to start the year, and his more tepid run of recent starts. I excluded changeups, as they’ve been put in play just ten times so far this year:

Sonny Gray First Five Starts
Sonny Gray Last Four Starts

(Source: Baseball Savant)

Perhaps surprisingly, both of his fastballs have continued to perform quite well, relative to league average. He’s completely retained the surprising gains made on his sinker last year, running it to a career-best 28% whiff rate, and while he’s still not doing much to leverage his elite spin into an elite fastball, it’s still been more than reasonably effective for a pitch that rarely breaks 95 mph.

No, Gray’s problem isn’t that he’s still relying too much on the four-seamer and sinker, as Michael posited, but his forewarning about those breaking balls was clearly spot-on. Even as he racked up strikeouts and quality starts early in the season, the level of contact he was allowing on the curveball and slider was clearly unsustainable.

Also visible is the irony inherent in baseball’s perpetually swinging pendulum. In terms of contact quality, his breaking balls have actually been a bit better than they were before! But that still doesn’t mean they were palatable. These things can manifest themselves in seemingly contradictory and often bitterly ironic ways — Gray’s tumultuous last couple starts have been littered with dinky hits like these — but now, I’m more inclined to view his recent troubles as chickens coming home to roost, rather than just a blip on the radar.

In short, Gray’s season is being unwound by an inversion of conventional wisdom. His fastballs, which theoretically have the low ceiling that accompanies his velocity, are keeping him afloat, while his curveball and slider, both of which typically check in as above-average pitches by both the eye test and results, are rapidly sinking him. So, what’s up with those breaking balls?

Unfortunately, a lot. On a technical level, they’re not super different, with spin rates, spin directions, and arm slots roughly in the same place as years previous. However, their  behavior continues to evolve, and not necessarily in a good way. Check out how their velocity and movement has changed over the past few years:

Both pitches have seen a substantial velocity drop, with the slider losing a full 1.5 mph despite the rest of his arsenal staying relatively stable. At the same time, the curveball has gradually become more vertical and less horizontal, while the slider’s side-to-side movement has only increased, now surpassing the curveball in that department.

I strongly suspect that for lack of time, I’ve missed some kind of mechanical or grip changes, because these are some fairly substantial profile shifts. That’ll have to wait until this website’s inevitable fifth Sonny Gray piece of 2020. But we can still talk about what the effects of those changes have been. And to put it bluntly, they don’t seem to be a good thing, for a few reasons.

Instinct tends to tell us that more movement is better, simply because it’s harder to hit something that moves a lot. Generally speaking, that’s correct. As always, though, context is king. Gray already has a big, arcing, bender of a curveball, and that’s not necessarily going to pair will with a slider that’s increasingly slow and slurvy.

Relatedly, the 2.1 mph velocity differential between the curve and the slider is easily the lowest of his career. They aren’t “blending together” in the traditional sense, which is when two breaking balls start to resemble each other in a way that blurs the distinction between them. Instead, the reduced velocity and increased horizontal movement on the slider means that hitters aren’t just getting more time to react to them, they may also be more easily distinguishable out of the hand, which will clearly make both pitches worse. Indeed, another selection of metrics indicates that hitters might just be seeing the breaking balls much better this year:

Are Hitters Better At Identifying Sonny Gray‘s Breaking Balls?

(Source: Baseball Savant)

Going left to right from column to column, here’s what we’re seeing. First, he’s throwing both pitches in the zone less. This could be by design, but as we’ll see in a moment, I suspect he’s rather having more difficulty commanding them like he did last year. That’s going to lead to some trouble, because naturally, hitters are taking fewer swings at those pitches overall. Most of them aren’t getting turned into called strikes.

This may be responsible for the perhaps misleading uptick in whiff rate he’s seen on both pitches, which have increased by about 5% each this year. They’re out of the zone more and therefore less likely to be hit, but as the very next columns show us, hitters aren’t chasing enough for it to be a good thing. Even though they are chasing the slider slightly more at an above-average rate, it hasn’t been to the effect one would like: the wOBA and xwOBA on those chased starters are among the three worst marks in baseball among qualified starters. The chase rate on his curveball, meanwhile, has dropped precipitously, which tells us that Gray is throwing far fewer competitive pitches, hitters are recognizing the pitch better than they have in the past, or a mix of both.

Finally, we get to swing rate and offensive performance on pitches over the heart of the plate. These can be highly informative, because they tell us how well a pitcher is doing when they miss their spot in the worst possible places.

As with chase rates, we see that while Gray has actually seen an improvement as far as some swing decisions go — he’s drawing fewer swings on sliders down the middle — only to see those gains wiped out by the contact that’s being made when they do swing. Also as with chase rates, hitters are just not letting Gray get away with any mistakes. When he leaves that bender over the heart of the plate, hitters are recognizing it, and they’re absolutely pounding it. As the wOBA shows us, this actually hasn’t even caught up to him yet in his bottom-line results! Unfortunately, it’s just another reason to be pessimistic about the Gray that might show up the rest of the year.

That wipeout curveball has been Gray’s bread and butter for the majority of his career. The slider has taken precedence at times, but qualitatively, most would tell you that the curveball is simply the better pitch. The slider has sent mixed messages, but it’s clear as day that whatever’s going on this year, Gray doesn’t have the curveball in the back pocket like he usually does. Heat maps of Gray’s curveball locations over the last two seasons should illuminate a lot:

He may have had some luck on his side last year, but when you can command a curveball as good as Gray’s to the bottom of the zone like that, you’re going to make your own luck. This season, he seems to have just lost all feel for the pitch, consistently missing either over the heart of the plate or, more frequently, down near the dirt, where it’s relatively easy for a hitter to not chase and make themselves look dumb. Not a recipe for success! As I said, given the recent fatigue and IL placement, I think there very well may be something physiological or mechanical going on, but unfortunately, I can’t speak to that right now. All we can do is watch him pitch tomorrow and see what happens!

I’m usually optimistic when it comes to player analysis. In these times as much as ever, it’s a lot nicer to focus on what players are doing well, rather than what they aren’t. I started looking at Sonny Gray wondering if I’d find some indication that he’d made the leap to being a true-talent ace, but it didn’t quite work out that way. Baseball’s pendulum is always swinging to and fro, but unlike Foucault’s Pendulum, there’s rarely much predictability as to what direction the next swing will go. Right now, I’m concerned that we’ve already seen the best of Gray this year, and that the pendulum will continue to push him in a direction we don’t like until he can make an adjustment and figure it out again. He’s done it plenty of times before, and I have faith that he’ll do it again. When that happens or what it looks like remains to be seen.

(Photo by Brian Rothmuller/Icon Sportswire)

Zach Hayes

Zach is a graduate student at Brown University focusing on sports, politics, and culture, and contributing baseball analysis at Pitcher List and Prospects365. Follow Zach on Twitter (@PineTarKeyboard) for periodic rants about Chicago sports and politics.

One response to “Sonny Gray Rides Foucault’s Pendulum”

  1. Avatar Rocket says:

    Interesting article. I would agree with your assessment that Sonny Gray has lived through several pendulum swings over his career. However, I do not think that we are currently seeing a swing back towards a downturn. He was sharp after his IL stint last night showcasing some nasty breakers and some lively fastballs. For example, he threw a curve to Ryan Braun a RH hitter that bounced on the front line of the LH batter box. Needless to say but, Braun was fooled badly and whiffed not even close to touching the ball.

    So that brings me to my point. Clearly, there was an issue with Gray’s back that he attempted to work through that had a negative impact on his stuff not being as sharp as his first several outings of the year. His outing before landing on the IL he pitched after a rain delay and in conditions in a downpour where he could not get a firm grip on the baseball. To a pitcher that relies on his breaking pitches he became a sitting duck facing the Cubs on 9/10. I think your article missed the fact that Gray is vulnerable to pendulum swings because of his confidence levels changing. When he pitches like he did last night, full of confidence he can overmatch most MLB players regardless of what the metrics are saying.

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