The Misguided Expectation of Linear Development
Why I can't quit MJ Melendez (yet)
Our brains (at least for baseball fans; I can’t speak for the rest of humanity) are hardwired to expect patterns. In the simplest of terms, a rookie who hits .260 in the Majors might then be expected to bat .265 in his second season, .270 in his third, .275 as a fourth-year player and so on.
Those numbers aren’t perfect examples, and maybe batting average isn’t the right stat to portray what I mean, but you get the idea: We expect young players to improve at a continued upward trajectory until reaching a plateau in their late 20s/early 30s.
But development in baseball is not always linear. This is why fans get frustrated when a player shows great promise (at times) in the minors, flashes (at times) in his early days in the Bigs and gets smoldering hot at the plate (at times)… before falling on his face and finishing his third Major League season with his worst OPS to date.
This is why fans are frustrated with MJ Melendez.
After being drafted out of Westminster High School in the second round of the 2017 draft, Melendez quickly established himself as one of the top prospects in Kansas City’s system. As early as 2018, MLB Pipeline ranked him fourth in the Royals’ system as a quality defensive catcher with a strong arm and big pop. He rose one spot to third prior to the 2019 season… then proceeded to hit .163/.260/.311 in 110 games at High-A.
Underwhelming as that season was for Melendez, perhaps even worse was the timing. It tanked his stock just in time for 2020 when COVID wiped out the minor league season, leaving fans wondering (for an entire year) whether he could bounce back.
He did. Across Double-A and Triple-A in 2021, Melendez rekindled the hope KC fans lost, swatting 41 homers with a monstrous .288/.386/.625 slash.
Even before reaching the Majors, his development and results were full of ups and downs, both offensively and defensively. When he reached Kansas City as a 23-year-old in 2022, the belief in his bat had returned. Since then, he’s provided three seasons of below-league-average production at the plate and moved full-time to the outfield early in 2023.
2022: .217/.313/.393, 97 wRC+, 24.5% K, 12.4% BB
2023: .235/.316/.398, 91 wRC+, 28.2% K, 10.3% BB
2024: .206/.273/.400, 85 wRC+, 25.1% K, 7.8% BB
Despite several torrid stretches, including hitting .273/.352/.485 in the second half of 2023, it’s admittedly puzzling (even for a believer like me) that he’s essentially gotten worse in each of his three Big League campaigns.
I say “puzzling” in the sense that, as outlined above, you’d expect him to improve from age 23 to 25 or, at the very least, remain stagnant. You might attribute his decline to various factors, like breaking into the Bigs at a young age, switching positions at 24 years old while facing the best pitchers on the planet or playing on bad teams (until 2024).
But the most obvious reason for his lack of success is the inability to put bat on ball. Despite a roughly league-average chase rate, he whiffed on 29.5% of swings last season — a 21st-percentile outcome. When you’re swinging at 52.3% of the pitches you see — 44th-highest among 286 hitters with 300 plate appearances in 2024 — that’s a lot of whiffs.
You can see above, via Baseball Savant, he struggles with pitches down and out of the zone, but that’s not all too uncommon when compared to the league average profile.
The bigger concern is at the top of the zone, especially pitches above it. If you watch a lot of Royals games, I’d bet you’re nodding along in agreement — just by the eye test, he’s always seemed to struggle with velocity up and these charts bear that out.
So why the optimism? How can MJ Melendez, after three Major League seasons, disprove the notion that development is linear, and at 26, he is what he is?
For one, as you might be aware, he’s worked this offseason to overhaul his swing. From videos he’s shared on Instagram, the new look appears more compact with his hands starting a bit higher. (For a better breakdown of the swing itself, I implore you to read Into the Fountains — Craig beat me to this topic this week!)
Perhaps most notable: a massive reduction in movement. It’s a much quieter load, one that may help him get to those fastballs that climb the ladder without leaving him exposed to offspeed offerings.
There are people much, much smarter than I am when it comes to hitting mechanics (hence why I plugged Craig’s work). Maybe a handful of GIFs of a new swing are more of a life raft for an optimist like me than they should be.
But the batted-ball metrics have mostly favored Melendez. When he makes contact, it tends to be loud, as evidenced by an 80th-percentile average exit velocity and 74th-percentile hard-hit rate in 2024, his worst Major League season. If he can make just a little more contact — and I believe he can, whether it’s due to new mechanics, better swing decisions or both — things could turn around in a hurry.
If you need an example to help paint the picture of non-linear development working in a hitter’s favor, a perfect example for Royals fans is should-be team Hall-of-Famer Mike Moustakas.
He rocked minor league pitching, struggled in his first few seasons with the Royals and was even *demoted to Triple-A* for about a week in 2014 before breaking out with a 123 wRC+ in 2015 and capturing the franchise’s single-season home run record in 2017. Oh, and he helped win a World Series along the way with clutch playoff moments in both 2014 and 2015.
I don’t mean to imply Melendez is destined to be a franchise icon, but there’s certainly talent simmering underneath the statistical profile. Derek Carty’s THE BAT X, regarded as one of the most accurate projection systems for hitters, pegs him at exactly league average for 2025 as a 1.0-WAR left fielder.
A .228/.308/.414 slash with 17 homers won’t get anyone too excited, but that’s simply a median projection. If nothing else, it shows there’s room for growth for a 26 year old, even if to some it feels like he’s out of time.