Carson Kelly is Raking

The NL West is a two-team division these days, but that wasn’t always so certain. In 2019, the Diamondbacks burst onto the scene as a potential playoff team — not the equal of the Dodgers, but a thorn in their side nonetheless. The Snakes didn’t boast the same top end as their Hollywood rivals, unless you had a wildly optimistic opinion of Ketel Marte, but they did have depth, personified by Carson Kelly, the highlight of their return for trading Paul Goldschmidt.

That 2019 season showed Kelly’s promise. In 365 plate appearances of platoon work, he compiled 1.8 WAR, combining competent work behind the plate with a 107 wRC+. That batting line was buoyed by a 13.2% walk rate and a juicy .232 ISO, neither of which seemed particularly convincing, but his central skills — good plate discipline, the ability to draw a walk, enough power to be respectable — all pointed to continued offensive competence.

The 2020 season wasn’t so kind. A .221/.265/.385 line was good for a 70 wRC+, and those flashes of light from the previous year — his walk rate and power on contact — both dipped. It was only 129 plate appearances, and it came with a .250 BABIP, so it was hardly a season he couldn’t recover from, but his swoon mirrored Arizona’s: 25–35, last in the NL West. After the Padres went nuclear this offseason and with the Giants continuing to hit on interesting players, it was easy to move on from the Diamondbacks and their bushelful of interesting but flawed players, Kelly included.

Secretly, though, Kelly’s 2020 was actually encouraging. Not the top-line numbers, mind you; those were terrible, like we talked about above. But consider: Kelly’s ISO (extra bases per at bat, if you’re unused to seeing that; it’s a measure of power) dropped from .232 to .164, and he totally deserved that. His barrel rate halved, his hard-hit rate declined precipitously, and he traded line drives and fly balls for grounders. Bad power central!

When he did hit the ball in the air, however, he started doing something right. There’s been a lot of talk about the air ball revolution: lofted swings, announcers screaming “launch angle” like a swear word, and the homer-or-bust mentality that pervades baseball now that pitchers are so dang unhittable. It’s a misnomer, though. What batters are actually talking about is a pulled air ball revolution. Allow me to duplicate a table you’ve surely seen before:

Yes, slug is in the air, but it’s in the air to the pull side. Kelly had all kinds of things go wrong in 2020, but he increased his air pull percentage from 30.4% to 36.4%. He might have been hitting the ball on the ground more, and with less authority overall, but he was getting to the pull side more often when he did make contact correctly.

Now seems like a good time to drop the big reveal: Kelly is fifth among position players in WAR so far this year. You’ll have to lower the qualification limits to see him, since he has only 54 plate appearances so far, but given that WAR is a counting stat, that’s even more impressive. He’s hitting .351/.537/.730, good for a 226 wRC+, and while that’s an unsustainable pace, he’s almost matched last year’s home run total in less than half the opportunities, and he’s doubled last year’s unintentional walk total!

First, let’s talk dingers. That pull form he showed in 2020 is even better this year: He’s pulled 42.1% of his line drives and fly balls so far. Now, that’s eight of 19, so it’s hardly a definitive sample, but it’s a mark in favor of the improvements he made in 2020 being real. You don’t have to be a prototypical power hitter these days to leave the yard, and four of those eight pulled balls in the air have accounted for three of Kelly’s four homers to start the season. A few of these goes a long way toward a solid offensive season:

That GIF wasn’t an idle example; it shows something else about his game. That minimal leg kick and flat swing aren’t new this year; that’s just how he swings. And it’s not the uppercut swing you’ve heard so much about, as Kelly hits the ball where it’s pitched. His power comes up in the zone, and luckily enough, that’s where pitchers are increasingly living.

In our heat maps, you can see a handy chart of slugging percentage per ball in play. Take the numbers outside the strike zone with a grain of salt, because the fewer balls in play, the more an outlier can affect them, but it’s clear that Kelly gets to more power high than low:

One thing that led to a low power output in 2020? He got away from swinging at the balls up in the zone. Take a look at how his swing decisions changed from one year to the next. Here’s 2019:

And then 2020:

It’s not a huge change, but his swing rate fell by three percentage points in the upper third of the strike zone and increased by six percentage points in the bottom third. That’s more grounders and less thump. There isn’t even a contact payoff: Kelly has whiffed in 18.4% of his swings in the bottom third of the zone, compared to 18.9% in the top third, over the course of his career. Most batters miss far more frequently in the top third of the zone because they’re swinging at four-seamers instead of sinkers. Kelly’s swing hits both equally.

This year, he’s swinging at a 2019 rate when pitches are high and swinging more than ever when they’re in the middle of the plate. That might not be enough to account for the increased power, but he’s also doing something else impressive when it comes to deciding whether or not to swing. On pitches that just miss the strike zone — defined in this case by the union between Baseball Savant’s “shadow zone” and pitches outside the strike zone — he’s turned from a marginally selective hitter into basically Mike Trout:

Yeah, that’s pretty good. Those pitches are the worst to swing at. Over the last three years, batters have been 4,877 runs below average when swinging at them, or 5.1 runs below average per 100 pitches. I can’t give you a good comparison to that, because that’s a worse performance than batters had against any pitcher in the game last year.

When you don’t swing, as you might imagine, things get better. It’s not like every take results in a ball — umpires miss calls with some regularity — but taking pitches just off the plate generates roughly three runs above average per 100 takes. That’s an eight-run swing per 100 pitches that you take instead of swinging at, though that might overstate it; if Kelly keeps up his current pace and plays a full season, he’ll turn roughly 50 swings into takes.

That’s neat, but Kelly is running a .537 OBP, and I’m not sure that a few tough takes account for him turning into peak Barry Bonds there. His 24.1% walk rate is a mirage. Even if you think his eye plays in the majors — I think it does, and a little newfound power won’t hurt it — he’s benefited from wild opposition so far.

On the first pitch of an at-bat, pitchers have located 22 of 54 pitches in the zone, a 40.7% rate. The leaguewide rate is 51.9%. Are pitchers simply staying away from his suddenly fearsome power? Not likely: He’s swinging at only 31.8% of first pitches even when they’re in the strike zone, 10 percentage points below average. On the other hand, you can’t exactly throw him a cookie and expect to get away with it:

Despite that cherry-picked clip, pitchers have been unsustainably wild against Kelly, and there’s no reason to expect that to continue. He has a good sense of the zone — no one would dispute that — but c’mon. He’s seen 10 2–0 pitches, and two have been in the zone. Walking is a skill, but pitchers have agency too, and the pitchers he’s faced have given him almost no choice. It’s take or swing at a bad pitch, and as we’ve already covered, he’s gotten much better at avoiding bad swings.

Am I overstating Kelly’s early-season breakout? Yes. It’s a good start to the season, and we’d be talking about him even without the walks. A batter honing his swing and getting to more power in the air is a tried-and-true trope, a good predictor of future success. The walks turn his statline into a caricature, but they’re indicative of good process, pitcher wildness notwithstanding. It’s too early to say for certain, but it looks like Carson Kelly might have put the best pieces of his game together and become a force at the plate as well as behind it.