The (d)evolution of Charlie Morton

2022 was probably not the season Charlie Morton wanted to have. After a mid-30s career renaissance that saw him consistently fall somewhere between “above average” and “elite, nearly best-in-class MLB pitcher,” 2022 was kinda junky. You might blame his recovery from a broken leg suffered during the 2021 World Series, or a rushed Spring Training in the wake of the lockout, though Morton himself probably wouldn’t. Whatever the behind-the-scenes explanation, though, 2022 was not great.

Morton posted a 108 FIP- in 2022, his highest since his pre-renaissance 2015 season, his last in Pittsburgh. The xFIP- was much better at 90 (that is, ten percent lower than league average), but still his highest in a full season since 2015. The strikeout rate hadn’t really changed from his prior renaissance seasons, and the walk rate was a bit higher, but as you can tell from that FIP-xFIP gap, the issue was homers.

You could, and should, be tempted to write off that gap as just a persistent swing of fly-balls-that-become-homers luck away from Morton’s benefit. With juicier balls, Morton’s 2017-2021 HR/FB rate was 12.2 percent, nearly identical to his first-year-in-Atlanta rate of 12.1 percent. The fly ball rate itself hovered around 30 percent in a fairly narrow band (28.9 percent to 33.6 percent, the latter coming in a short season). But then came 2022, with relatively deadened balls, and somehow, Morton’s propensity to the gopher ball grew. His HR/FB rate shot up to 16.5 percent, his highest since 2010. That in and of itself wouldn’t be killer, except his fly ball rate also skyrocketed, up to nearly 40 percent — not just a career high, but an egregious jump from anything he had experienced previously. Leaguewide, fly ball rates slightly budged up between 2021 and 2022, while the HR/FB cratered down over two percentage points, from 13.6 to 11.4 percent. Morton’s experience was swimming upstream from the leaguewide flow, to his detriment.

From whence those extra 2022 homers? A couple of things jump out. Morton has multiple pitches, but he’s a largely a two-pitch guy, throwing lots of curves and four-seamers. Between 2021 and 2022, neither his average launch angle nor his fly ball rate on his curve budged... but the fastball rates skyrocketed. His fastball fly ball rate nearly doubled, to right around 40 percent. Beyond that, though, Morton experienced a revenge of platoon splits.

Between 2017 and 2021, Morton actually exhibited some degree of reverse splits: a 3.33 FIP / 3.63 xFIP against righties, and a 3.15 FIP / 3.19 xFIP against lefties. The difference was driven almost entirely in strikeout rate, as he struck out just about a third of lefty batters faced. In retrospect, this is kind of a bizarre outcome. Platoon splits tend to be larger factors for pitchers who rely on horizontal motion; one-plane, straight-down curves aren’t much of a platoon-problem pitch. Yet, Morton’s calling card has been the extreme sweep of his curve and the way it plays off a poorly-”rising” but great-fading four seamer to create an extreme horizontal location differential, which suggests sizable platoon weakness, but one that never materialized. Anyway, fast-forward to 2022, and...

• 2022 vs. righties: 3.41 FIP, 3.13 xFIP. Hey, this is quite good!
• 2022 vs. lefties: 5.11 FIP, 4.09 xFIP. Uh-oh.

So long, reverse splits. Hello, sizable left-handed batter problem. In brief, and while I took over 500 words getting here, oh well: Charlie Morton’s 2022 struggles were a lefty homer problem. In fact, Morton’s fly ball rate against righties last year was just around 32 percent, which is maybe a bit high for him but not so much so. His fly ball when facing a lefty last year skyrocketed to 45 percent. That’s not an insane rate in a vacuum, just 30th among the 150ish starters with the most lefty batters faced last year, but it was a complete deviation from his past batted ball profile.

Perhaps another way to think about it is to think about homer rates:

That’s a lot of homers (by lefties)!

Alright, whatever, why did I spend so long talking about 2022? Because, well, we’re in 2023 now, and here’s how Morton has “evolved” in his small, current-year sample size.

• FIP-: down, from 108 to 95
• xFIP-: up, from 90 to 100
• Fly ball rate: down, from 38.6 percent to 33.6 percent
• Homer rate against lefties: 3.4 percent, down from 4.9 percent, but still higher than before
• Strikeout rate: way down, from 28.2 percent to 21.9 percent
• Walk rate: up, from 8.7 percent to 9.6 percent

The strikeout and walk rates are the worst, so far, in his renaissance period. The xFIP- is therefore also his worst since 2015.

As to what’s changed, quite a lot, though not all of it answers the question.

The curve is harder. Over the past few years, including through his Braves tenure but starting before that, Morton has added ticks to his curve. This has compromised its movement profile, because harder pitches have less time to move, and made it more like a slow slurve. Morton’s curve used to have about double-or-more the horizontal break of an average curve, now it’s down to about 1.5 times as much. For the most part, the location of Morton’s curve is also different.

To righties, Morton used to just hammer the same low-and-outside corner pre-2022, struggled to locate it as well in 2022 such that sometimes it was more over the middle and sometimes more down-and-away. In 2023, he appears to be compensating for less movement by essentially throwing it as a chase pitch, rather than a pinpoint, you gotta swing but can’t really hit it if you do pitch.

To lefties, Morton kinda-sorta backdoored the pitch and occasionally backfooted it. This year, the backdooring is gone and it’s mostly just coming in on the bottom edge. 2023 again appears to a case of compensation by putting the pitch somewhere where it’s harder to make good contact.

Looking at this, you might be somewhat puzzled — why did lefties torment Morton so much in 2022 when his curve location was similar enough to 2021? The answer is a non-answer here: the curve wasn’t the reason for the lack of effectiveness to lefties. More on that later. In the end, though, Morton’s curve has lost a lot of whiffs between 2022 and 2023, but generally maintained its effectiveness. The xwOBAs and launch angles are nearly identical between the two years despite the lower whiff and put-away rate, suggesting that Morton is just getting easy outs early in the count with the curve instead of the same level of swing and misses. The location change appears to be compensating for the different movement profile here, though it’s not actually clear why the change to movement profile was warranted.

So, it’s the fastball, then? What else could it be? Morton’s four-seamer was more than fine against righties last year. He threw it middle-middle to middle-away off the plate, allowed a 34 percent fly ball rate on the pitch, and got whiffs on over a quarter of batter swings, all totaling to a .314 xwOBA. Against lefties, it was far more of a problem: a whiff rate of just 16 percent, an average launch angle of 24 degrees, a fly ball rate over 42 percent, and an xwOBA of .365. The location was honestly pretty similar to what he did in 2021 — middle away, with specific pockets — but less “away” and more consistently over the plate. The pitch lost a fair bit of its horizontal motion relative to 2021, which probably explains this: four-seamers meant to fade away to the outer edge of a lefty batter’s zone just... didn’t, and were ripe for the mashing.

This explains 2022, but not so much 2023. The 2023 heatmap seems like the 2022 heatmap but maybe worse in some ways, yet Morton’s fly ball rate on the four-seamer to lefties has fallen all the way down to 17 percent, and his average launch angle is down to nine degrees. It’s hard to square those things with the heatmap, and it might be a small sample size, but it also might be related to the fact that his four-seamer is now basically a sinker. Check it out.

If you compare this to 2022 or 2021, you can possibly squint and say, “Hey, no wonder hitters are hitting it into the ground, it’s coming in even lower than they’d figure.” Of course, the problem is that they’re still hitting it hard: an average exit velocity of nearly 93 mph by lefties against the four-seamer, and a .378 xwOBA. With this infield defense, that doesn’t seem particularly gratifying. But the homers are staying away, for now.

So, where are we? Morton is throwing his curve harder and in a different location, but the curve was never the issue. Lefties crushed his four-seamer for many homers last year, and some of that may have been HR/FB, but some of it may have also been movement-related. This year, the change in movement may be stifling homers to some extent, but it’s not actually stifling hard contact. Meanwhile, Morton’s whiff and strikeout rates are down on almost everything across nearly every useful split, and his walks are up, largely as an artifact of fewer chases (almost entirely by lefties, probably because he no longer throws tempting backfoot curves) as opposed to more bad misses.

So, where are Morton and the Braves now? Of course, he can still change, evolve, and so on over the rest of the season. But right now, he and the Braves appear to be in a spot of trouble. While the homers haven’t come yet, the four-seamer doesn’t seem better against lefties in a sustainable way, though I suppose he could keep it going as long as hitters continue to swing over the four-seamer-that’s-a-sinker. The curve is fine even if it’s changed, but there’s no way that lower whiffs are a good thing for him, and the reality is that his FIP against lefties in the early going is still over 5.00. The four-seamer’s whiff rate against righties has also cratered.

The net result is that right now, Morton is just an average-y starting arm with platoon issues that have persisted through a full season, whose line looks better than it should because of some karmic payback for an elevated HR/FB rate last year. In a vacuum, this isn’t a problem: an average arm gives you a decent chance to win, and with the Braves’ offense, they can ride that sort of arm to great success. But, when that average-y arm is one of your team’s only three starters, the issues start to pile up. Morton becomes less and less tenable to leave in the game against good lefty batters, or even allow to face lefty-heavy lineups in key contests, but what other options are there? Turning back Morton’s clock to 2021 seems desirable, but isn’t realistic.

So, we’ll hope for the whiffs to come back and the HR/FB to stay low, or for Morton to figure out a way to use his new profile to solve lefty batters. Because the alternative seems like it could cave in on the Braves’ heads pretty badly at this point.