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Why does Alex Jackson strike out so much?

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The Marlins catcher won’t be a playable big leaguer unless he gets his K% under control.

Alex Jackson #23 of the Miami Marlins in action against the New York Mets at Citi Field on August 31, 2021 in New York City Photo by Jim McIsaac/Getty Images

The Marlins’ trade deadline acquisition of Alex Jackson was unpopular yet somewhat understandable. Above all else, the franchise was determined to upgrade at the catcher position. Why not roll the dice on a former first-round draft pick who had been thriving at Triple-A? It did cost them veteran Adam Duvall, but they didn’t value his production for the rest of 2021—having already fallen out of postseason contention—and believed his spot could be filled in future years either via homegrown corner outfielders or free agency.

Jackson made his Marlins debut on August 2. Exactly three months later, the Braves clinched the World Series title, with Duvall as an everyday starter. That would’ve been easier for Marlins fans to stomach if Jackson had shown any inkling of being The Guy to remedy their issues behind the plate. Instead, the 25-year-old limboed below the lowest bar imaginable: Jackson slashed .157/.260/.278 with Miami (55 wRC+) and performed below replacement level overall. He was a downgrade for them.

Jackson was the Marlins’ most-used catcher down the stretch. The front office explicitly admitted that wouldn’t be good enough for 2022 when they nabbed Jacob Stallings from the Pirates. Although Stallings clearly has vaulted to the top of the depth chart, there will be ample playing time available for his backups. Can Jackson capitalize on it? This is something Fish Stripes will discuss more comprehensively once the dust settles on the MLB offseason and we do our usual series previewing the upcoming campaign.

For now, I’m fixated on Jackson’s nasty strikeout habit.

Alex Jackson strikes out swinging against a high fastball from former teammate Ian Anderson

Combining his time with the Marlins and Braves from 2019-2021, Jackson has struck out in 47.4% of his major league plate appearances. According to FanGraphs, it’s the highest rate for any non-pitcher in modern MLB history (min. 100 PA).

You might be thinking, “cut the kid some slack! It’s tough to adjust to The Show.” Well, I ran a query with the span finder at Stathead regarding players at the start of their Marlins careers (including both rookies and newly acquired vets). Jackson’s 60 strikeouts following the trade are the most ever for any non-pitcher through their first 42 games as a Marlin. He tops the list despite frequently batting near the bottom of the lineup which limited his PAs:

  1. Alex Jackson, 60 K (123 PA)
  2. Giancarlo Stanton, 58 K (169 PA)
  3. Jorge Alfaro, 56 K (160 PA)
  4. Lewis Brinson, 53 K (156 PA)

Also, he’s not exactly a “kid” anymore. Jackson entered professional baseball seven-and-a-half years ago and had three separate seasons at Triple-A to prepare for this first real opportunity. He was older in 2021 than Alfaro was as a new Marlin. Ditto for Brinson. He had an extra half-decade of life experience than Stanton.

We can see that something is very, very wrong with Jackson. Even in this small sample, his sky-high strikeout rate cannot be excused, and it cannot be tolerated moving forward if he hopes to stick in the big leagues in any capacity.


Why is Alex Jackson getting punched out so frequently? Let’s consider where he stands relative to his contemporaries, who I am defining as non-pitchers with 100-plus MLB plate appearances since 2019. There are 624 players in this bucket, per FanGraphs.

Jackson ranks dead last—624th out of 624—in contact rate, at 51.4%. Will he put his bat on the ball? It’s essentially a coin-flip proposition every time he swings, and keep in mind that is inflated by foul balls. As is the case for everybody, Jackson is better at connecting with pitches in the strike zone than those outside of it. But a lack of selectivity is placing him at a disadvantage—his chase rate is extremely high (ninth percentile in MLB). Those swing decisions are often putting Jackson in bad counts or finishing him off altogether.

Above all else, A-Jax has a timing problem. Major league batters in general feast on four-seam fastballs, which arrive at home plate with slightly higher velocity than any other offering but with less movement. Particularly deep into a plate appearance—down to their final strike—they’re rooting for a straight heater that can be put in play.

However, Jackson is an anomaly: he whiffs even more than usual against four-seamers (58.7 Whiff% in 2021). He has only three hits in 52 career at-bats ending with that pitch type, according to Baseball Savant. That’s a lower batting average (.058 BA) than any other big leaguers with similar opportunities during that span, including pitchers like Sandy Alcantara (5-for-46, .109 BA).

There are, unfortunately, numerous examples of Jackson showing up late to four-seam fastballs that caught plenty of the plate:

Jackson utilizes what I’d consider a modest leg kick by today’s MLB standards—the heel of his front foot doesn’t rise more than six inches off the ground. It is more like a glorified toe tap. Yet he’s having difficulty getting it down quickly enough to complete his swing against MLB-caliber velo.

Here is a slowed-down side view of Jackson striking out vs. Anthony Banda of the Pirates. Jackson has the platoon advantage as well as the edge of familiarity. Banda just threw him three consecutive fastballs prior to this! At 94.9 miles per hour, the putaway pitch’s speed was roughly average by MLB reliever standards. Alas, Jackson is soooooo late that the ball is almost in the frame once his foot finally lands.


Throughout his Minor League Baseball career (501 games), Alex Jackson struck out at a 29.5% clip. That swelled to 32.9% in his 150 games at Triple-A, but had been trending in the right direction when he repeated the level in the Braves organization earlier this season (28.5%). It’s hard to overstate how much his outlook for 2022 and beyond would improve if he could somehow dip back into that range against MLB opponents.

Perhaps new Marlins hitting coach Marcus Thames has some ideas to address Jackson’s mental and mechanical flaws.