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Is Carson Kelly’s offensive emergence real?

The Arizona backstop has been one of the league’s best hitters to start the year, but how much of it is sustainable?

MLB: Arizona Diamondbacks at Atlanta Braves Brett Davis-USA TODAY Sports

In Major League Baseball, there lies a dearth of premium offensive talent that materializes from behind home plate. Over 300 players have recorded at least 50 plate appearances in 2021. Of the top 50 in wRC+, only four are catchers (Buster Posey, Carson Kelly, Yadier Molina, and Tucker Barnhart; Yermín Mercedes doesn’t count). You have to go to no. 65 before you have another (Sean Murphy). Posey and Molina aren’t really surprises at this point, and, to a lesser extent, neither is Barnhart. Kelly, however, is a far more intriguing piece here given the early production.

The Arizona Diamondbacks have been one of the surprising teams early in the year in the sense that they’re playing .500 baseball and featuring just enough offensive talent to prevent the general public from forgetting they exist. Carson Kelly has very much driven the Arizona bats to a top 10 standing in virtually every statistical category that should make their fourth-place finish in the National League West that much more fun to watch.

You might remember Carson Kelly as part of what was thought to be a fairly underwhelming return for franchise cornerstone and (at the time) impending free agent first baseman Paul Goldschmidt. It was Kelly, Luke Weaver, and Andy Young who served as the players relocating to the desert in that trade. A reassessment of the deal now might view it as a touch different given that the trio have all appeared on the Major League squad this year, but perspective can really change dramatically if Kelly specifically keeps going in the way that he is.

Kelly has shown flashes of being a competent bat at baseball’s top level in his three seasons with the Snakes. The 2019 campaign was especially strong, where he posted a wRC+ of 107, a .232 ISO, and a .348 on-base percentage, while making hard contact at a 48.7 percent rate. He faltered pretty significantly in 2020 virtually across the board, as so many did, leaving little indication that a breakout such as the one he showcased in April was on the horizon.

But in 2021, Carson Kelly has been one of baseball’s best, regardless of position. Among all position players with at least 50 PAs—an arbitrary number, but it feels too early in the year for Qualified—Kelly’s fWAR (1.4) ranks 14th and his wRC+ (195) ranks seventh. His ISO easily eclipses anything he’s done in the past, at .333. He’s walking at an 18.3 percent clip, putting him in eighth, against a strikeout rate that comes in at just 14.6 percent. It all culminates in a line that goes .333/.476/.667/1.142 across his first 82 plate appearances. By any measure, it’s a great start for Kelly. But, as is inevitably the case with any replacement level-ish player off to a hot start, the question immediately transitions to the sustainability of it.

Kelly’s BABIP, seemingly always the first indicator of regression, is at .311. Not wild. His hard hit rate sits at 41.2 percent. Not as high as his 2019 campaign, but a figure that still works in his favor, especially with a groundball rate at 29.4 percent, a significant drop from last year (41.9) and the lowest of his career to this point. The walk numbers indicate this enough, but he’s been patient (Swing% at 38.2, a decrease of over seven percent from last year), and his Chase%, at 18.9, ranks in the 90th percentile.

Baseball Savant also has Kelly at a .314 xBA and a .468 xwOBA, both of which continue to enhance the idea that even with slight regression (especially in regard to the OBP), Kelly can continue to maintain his pace among the league’s best offensive catchers. His numbers to this point aren’t a complete anomaly, at least.

However, a key element of all of this to consider is Kelly’s opposition up on the bump. And it’s hear that we start to develop some apprehension over just what Kelly can maintain over the course of the full 2021. Ben Clemens over at FanGraphs wrote up a bit on Kelly’s start a couple of weeks ago, exploring Kelly’s pitch selection (specifically in relation to the strikezone) and found some trends that don’t necessarily bode well:

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

The article is linked above—and the numbers have, of course, changed a little bit just due to the nature of time—but the passage here is certainly a wrinkle in terms of hope for Kelly’s sustainability after this start. His approach is true, and he’s obviously been making quality contact, but opposing pitchers have been brutal against him. Especially on that first pitch. Of all trends to consider in the midst of this start, that one seems most likely to come to a swift and bitter end. Easily. By miles. But how much it ultimately affects him in the grand scheme of the numbers remains to be seen.

There’s also the matter of those contact trends. The Hard% is solid on the surface, but doesn’t offer much in terms of genuine effect when stacked up against other hitters. It ranks in just the 43rd percentile, while his average exit velocity falls in the 30th. And while those specific contact numbers don’t appear to be affecting his BABIP or anything of that nature, it is a pretty large drop from 2019, when it was at almost 49 percent. The longer the season wears on, the more difficult it could be to outplay some of the rather average type of contact.

It almost seems very paradoxical. Virtually everything that we look at with Carson Kelly would seem to indicate that he’s in really good shape moving forward. Slight regression? Sure. Most players reaching base at a .470+ rate are marked for it. But that last element, where he’s starting with a legitimate advantage due to the struggles of opposing pitchers, kind of starts to sort of unravel it. Better competition over the course of the season—at the very least—transforms it from a potentially mild regression to something that is much more unknown.

Even if that advantage is the case, though, it’s hard to imagine too steep a dropoff for Kelly. If anything, an increase in competency from opposing pitching will harm his walk rate more than anything else he’s done. As Clemens notes in the above piece, Kelly is very good about allowing the pitch to do a lot of the work for him. So continuing to be aggressive on those pitches in the upper portions of the zone is going to allow him to not only continue to make fairly good contact on a consistent basis, but also to avoid the groundball in the way that he’s been doing so well to date.

Ultimately, is Carson Kelly a top 10-15 hitter in all of baseball? Probably not. And as the walks come down, it’s likely that many of his outputs will as well. But the power seems legitimate enough. Kelly’s approach works to his benefit, and while some of the whiff tendencies may return, his zone awareness is a boon to his offensive game. Combine that with defensive abilities that largely rank among the top catchers in baseball, and suddenly the Diamondbacks have a new cornerstone to replace the old one. It just took a couple of years to realize it.


Randy Holt is a contributing writer for Beyond the Box Score.