Let’s Get Small: Hundreds of Minor Leaguers Have Shrunk

Once all the blurbs for a prospect list have been written, I comb back through the giant spreadsheet that populates what readers see on The Board and double check its many fields for errors and inconsistencies. Two data points I’ve kept manually since 2017 are the heights and weights of the prospects who have passed through that space. At times, this has felt nonsensical — there are heights and weights on our player pages, and they could easily be pulled into the machinery that pumps out the tables that accompany the write-ups you see on our lists. But players’ measurables, especially in the minors, are often obviously wrong, and so for a little over a half decade, I’ve used my own judgment to make manual adjustments in cases when what is listed is clearly incorrect.

This has mostly meant manually adjusting players’ weights as they’ve gotten older and bigger, because even when players are on big league rosters, there is sometimes radical imprecision around their actual specs. When it comes to heights, however, I’ve overwhelmingly deferred to those on minor league player pages unless there was an egregious under-reporting (I think Oneil Cruz was the last one I manually fudged). Once the 2023 minor league season began, my pre-publication checks revealed a strange pattern: Many minor league players, mostly hitters, were suddenly listed on minor league player pages as being one or two inches shorter than my previous records indicated, and some of them had shrunk by as many as four inches.

While incorrect heights and weights are prevalent, widespread change to them across the entire player population was strange and struck me as probably having a cause. I’m going to show you the list of changes to players’ heights and go over potential explanations for how and why this has happened (and why so many heights were wrong in the first place), but first let’s talk about why this is an important detail.

Player measurables are a basic biographical staple in every sport, wherever you look, spanning decades. “How big is that player?” is a fundamental question any sports-watching person might ask when size (and what it enables) is often a component of success. Professional sports franchises should publish accurate biographical information for its own sake.

In contemporary baseball, player height was perhaps as important a variable as ever this year because, for part of the season, it was being used to determine the strike zone for the Automated Ball-Strike System (ABS) at Triple-A. Teams also use measurements in player evaluation. They’re on every hard-copy roster passed around at showcase events and backfield games, helping to identify and assess players who are often in nameless jerseys. They’re also sometimes a variable in more objective means of assessment, like pro scouting models that use listed heights as one of their many inputs.

I’ll talk more about each of these key areas later in the piece, but right now, readers should consider some caveats. First, the only players included in this sample are those who were ranked on a prospect list in a prior year and then were ranked again in 2023. I only had cause to update heights and weights if a player remained on a list this year, and I was only able to log a change when I had a previous height and weight in my records to compare it to. Players who were totally new to The Board were not included. It’s possible the heights of players for whom I did not keep a previous record have changed and gone unnoticed. Conversely, players who used to be on The Board but aren’t any longer, like graduates or players who fell off of prospect lists, are not captured here, though many of their heights have also changed. I save the biographical records of the prospects who fall off The Board, and while I didn’t comb back through the 1,000 or so ex-prospects I’ve stored to look for more changes, a quick glance revealed that many of them also shrank by one or two inches.

Another caveat to keep in mind is that I’m just a guy, a fat-fingered idiot capable of mis-entering someone’s height in my spreadsheet in the first place. That’s not a reasonable explanation for the scale of the changes you’re about to see, but it might be why any individual player’s height is significantly different than before. You can use the Wayback Machine to check my work, and in many cases the disparities I show below can be cross-checked using the listed heights and weights in team media guides compared to what’s listed on current player pages. There’s also a lag between when a player’s measurables are updated, and when I notice that update and change them in my database. It’s possible that not all of these changes actually occurred in 2023, but instead are ones I missed in the year or so prior.

Any one of these could just be a data entry flub on my part, but not all of them. We’ll get into some potential explanations for this phenomenon shortly, but first, here’s a very large (sortable) table of height changes. Player heights are listed in inches:

To get to the bottom of how this sweeping trend came to be, I reached out to several player development executives and sources with Major League Baseball (all of whom spoke on background for this story) to learn how and when players are measured, how those measurements come to be displayed on the internet, and if either process had changed because of adjustments to the ABS zone at Triple-A and in the Low-A Florida State League this season.

According to all parties, MLB sent personnel to teams’ camps during 2023 spring training to officially measure minor leaguers so that they could use accurate heights to draw the vertical boundaries of the ABS zone. Previous reporting by Baseball America indicated that 27% of a player’s listed height determined the bottom of his strike zone, while 51% of that height determined the top. Recent writing from The Athletic’s Jayson Stark revealed that players and other parties believed this methodology led to a higher-than-desired strike zone, so MLB quickly changed course and recently sent teams a memo notifying them that the Hawk-Eye optical tracking technology installed at every Triple-A ballpark to facilitate ABS would now be identifying and using checkpoints on hitters’ bodies to draw the top and bottom of the zone. This began on September 5.

During reporting for this piece, I learned details about the new zone that are ancillary to my player height project but I think will be of interest to readers. Hawk-Eye is currently using the crook of the hitter’s rear knee to draw the line at the bottom of the strike zone, and, as Stark has already reported, one baseball above the belt to draw the top. Hawk-Eye is now taking a snapshot of the hitter’s body position at the moment the baseball is midway across the plate (the same location used when evaluating umpire performance) and is then utilizing a rolling average of those snapshots across the hitter’s 50 most recent plate appearances to determine the hitter’s zone.

The zone is not dictated or impacted by a batter’s stance prior to the pitch being delivered, so hitters can’t artificially shrink their zone with a wider stance that compresses the gap between their knees and belt, nor are players who use a more upright stance punished with a larger zone for doing so.

Back to the topic of shrinkage. There were conflicting accounts of the independent spring measurement process. MLB sources indicated to me that an effort was made to measure as many minor leaguers as possible in each organization. But while my sources with teams that train in Florida all corroborated this, my sources with teams that train in Arizona had a more mixed experience, as some in the Arizona contingent said that only players who could reasonably be expected to make it to Triple-A were measured, not those in the very low minors. One executive with an organization that had several lower-level minor league players’ heights change told me they only recalled MLB measuring their team’s upper-level hitters; multiple player dev folks in Arizona claimed that not all of their minor leaguers were measured.

In addition to every Triple-A affiliate utilizing ABS in 2023 — the Pacific Coast League has been using ABS since Opening Day, while the International League began utilizing it April 25; half the games employ full ABS, while the other half make use of an ABS-aided challenge system — most teams with training complexes in Florida also have a Low-A Florida State League affiliate that has used ABS to some extent during the last several seasons. It was much more likely that prospects passing through Florida-rooted farm systems would play at an affiliate using ABS at some point during the season. Other than Cincinnati (which has an FSL affiliate in Daytona), minor leaguers in Arizona-based orgs don’t encounter ABS until they’ve reached Triple-A, so I can see the logic behind MLB wanting to collect a very complete data set in Florida, but being comfortable with a more limited, precise, and easier-to-obtain set in Arizona. Still, there are so many lower-level hitters from Arizona-based orgs who shrunk that I think it’s fair to conclude MLB got as many hitters as they could.

Sources indicated that while MLB measured the players, the teams were then given the measurements and tasked with inputting them into eBIS, the portal through which MLB transactions are carried out and in which official biographical information is stored. If a rehabbing big leaguer played at an ABS affiliate, it was left to the club to update his height information to comply with ABS. I could find no instances in which a rehabbing big leaguer’s measurements changed during a Triple-A or FSL assignment, which could indicate there was non-compliance in this area if MLB did in fact ask teams to measure their own rehabbers. But I wasn’t able to use archive.org to check for changes to the player pages for every rehabber from the height-driven ABS era; I gave up after 17 fruitless tries, all from late April, when I thought the request/mandate to measure rehabbers would still have been new enough to be adhered to.

Sources with the league indicate that for minor leaguers, the heights and weights we see online are coming from inputs in eBIS, while for major leaguers, those heights and weights are supposed to be coming from the team media guides. But while the media guides themselves often appear updated, MLB’s player pages and online rosters are often not, sometimes resulting in significant discrepancies.

While I think it’s fair to say that the record-keeping around players measurements at the big league level is rather lax for a major pro sport, I also think there’s enough here to conclude that, while likely still imperfect, the listed heights for current minor league hitters are more accurate than before, and probably more accurate than they will ever be again, since the MLB pilot program to collect player measurements likely won’t continue now that listed height no longer seems like it’s in the mix to dictate the ABS strike zone.

Having determined the process by which players are measured – and how those measurements are reported – let’s consider why so many heights seem to have previously been inaccurate.

Eliminated Explanation: Teams lowered players’ listed heights in attempt to gain an advantage in a world of ABS.

Unless club personnel were knowingly inputting lower-than-accurate heights into eBIS after the MLB pilot program handed over measurements, the order of operations here prevents us from concluding that teams tried to do this, juicy as it may be. So long as we trust that MLB’s measurements made their way onto the player pages, any team-driven inaccuracy, intentional or not, had to occur prior to teams being told that height-drawn zones were being put in place.

Potential Explanation No. 1: Amateur players have tended to overreport their heights, teams weren’t compelled to update them until this year, and now many of them are accurate.

Because an overwhelming majority of the changes are just one inch, this strikes me as the likeliest explanation for why so many individuals shrunk. Or more specifically, why any one individual shrunk. Up until MLB’s brief pilot program, there doesn’t appear to have been any regulation around the way the heights and weights of players at any level were reported. MLB maintains player pages with biographical info for lots of amateur players, and it’s understandable that it would be difficult to make those pages universally accurate because they’re dealing with players from all kinds of different schools, all over the continent. Meanwhile, the transfer portal presents its own challenge for keeping records like this up to date and accurate.

Whether or not teams could be bothered to both measure their newly-acquired (drafted, signed or traded) players and update eBIS seems to have been highly variable. But it’s pretty reasonable to think that players who were measured with their shoes on (and who may have embellished their height by an extra inch at some point in the past) would lose two inches when they were officially measured, barefoot, by MLB personnel.

Potential Explanation No. 2: Teams had either previously been derelict in reporting their own players’ heights, or had been overreporting their players’ heights intentionally, perhaps to influence opposing teams’ pro scouting models.

Because there are clear trends occurring here — some clubs have players more consistently shrinking two inches or more, while others have almost none at all — some version of this explanation (in which teams were knowingly disseminating incorrect measurements for whatever reason) probably applies to at least a few teams. From previous conversations I’ve had with scouts and executives, I deduced (and later confirmed) that player height is often a variable in pro scouting models. It probably has a small impact — these models have many, many inputs — but I know of a trade in which a team received a player who turned out to be much shorter than his listed height, and the way the model would have otherwise projected him was different enough that he would have fallen behind other candidates in the model had it known he was 5-foot-7. Hilariously, the listed height on his player page (he plateaued at the upper levels and has fallen off prospect lists) has not changed; he’s still listed as several inches taller than his actual height.

If teams know that their own model essentially “NPs” (meaning, assigns a non-prospect grade) players who don’t meet a certain height requirement, they can deduce that other teams’ models might as well and fudge the heights of their own guys to boost their value in trade discussions. This may be why some of the shortest players in my sample experienced the biggest changes in height. League-wide record keeping has probably been messy enough in this realm that it isn’t a good idea for teams to trust listed heights as an input in their models at all.

Potential Explanation No. 3: Players, including some who had previously overreported their own height, found a way to be as small as possible during the official measurement process.

Something like this, or some other kind of significant measurement error, has to be the explanation for some of these three- and four-inch changers, right? Every two fewer inches of height meant 17 square inches of area would be shaved from your strike zone; the one inch of vertical zone multiplied by the 17-inch width of the plate. It would be tempting to stand with awful posture for 30 seconds while you’re measured in order to have a meaningfully smaller strike zone all year. It’s possible MLB personnel prevented hitters from doing this with an in-the-moment “tsk tsk,” but given that they were trying to measure dozens of guys and quickly move on to the next camp, it’s feasible some sleight of spine occurred.

Even though I think methodology (shoes on or off, slouched or no) and single-inch exaggeration are largely to blame for much of this phenomenon, the players whose heights changed substantially deserve some case-by-case analysis. Here are screengrabs of the four-inch shrinkers and a few select three-inch changers, followed by my entirely unscientific thoughts on each case.

Brooks Lee was listed at 6-foot-2 on his college player page and upon entry into pro ball, but is now listed at 5-foot-11. Forced perspective is contributing to him looking nearly even with Jason Vosler in this photo, and once you account for the thickness of his helmet, I guess I buy that he’s 5-foot-11.

Carlos Colmenarez’s gap seems to have been caused by a data entry error on my part. MLB.com’s Jesse Sanchez had him written up as being 5-foot-10 in his amateur reports, and Colmenarez’s player page upon entry into pro ball also had him listed at 5-foot-10. He’s clearly a few inches shorter than Jonathon Long.

Tyler Black is listed at 6-foot-2 on his Wright State player page (the source of my initial Board input prior to him being drafted) and was 6-foot-1 in the Brewers media guide entering the season. Before I learned about MLB’s pilot program, his 2023 shrinkage to 5-foot-10 felt suspect to me, because Black was one of the players who seemed most apt and eager to use the ball/strike challenge system in the 2022 Arizona Fall League. Walks are a substantial part of his skill set. It was tough to find a satisfactory moment to screengrab Black upright and close to another player on the field, so I’ve included two above. He also stands next to Pedro Pagés and Andy Thomas, both listed at 6-foot-1, several times in my video from last year. I’m finding it quite tough to actually gauge how tall this guy is.

Brennen Davis was listed at 6-foot-4 entering the year and, while it was frustratingly difficult to find a useful moment to screengrab, I don’t think his current listed 6-foot height passes the smell test. Watch as he crosses home plate and is greeted by Sergio Alcántara, who is somehow listed at 6-foot-4, a full seven inches (!!) taller than his previous listed height, which absolutely has to be an error someone made inputting his height into eBIS. Both Davis and Alcantara (seriously, seven inches?) appear likely to be data entry errors, maybe even ones that were swapped with one another.

Here are the two short kings. The gap between them and their counterparts in these photos is so large that it’s tough to gauge exactly how much height difference there is between them, but I bet both of their current listed heights are accurate.

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For a major professional sport, the amount of imprecision around basic back-of-the-baseball-card information is disappointing, even though it appears MLB’s pilot program generally made listed heights in the minors more accurate. I know the overwhelming majority of baseball fans, even the nerds who read this website, don’t especially care whether or not these heights are accurate, but for those of us trying to use information like this to better understand the game and its players, it’s frustrating and somewhat troubling.

There are opportunities for MLB to collect accurate heights and weights of players entering pro ball at the Draft Combine and via USA Baseball and PDP activities, but according to a source with the league, the information from the Combine is not uploaded onto the league’s draft tracker nor to player pages. Finding a way to make that happen is the easiest and cleanest way for us to at least start with correct measurements as the players enter pro baseball.

I can’t offer a great solution for the problems with inaccuracy that occur after players have assimilated into pro ball, however. In the past, reporting heights and weights was left to the teams to complete on a sort of honors system, and whether clubs would post accurate info has varied substantially based on the care and competence of the people tasked with doing it for each org. Continuing a version of the MLB-led 2023 program that resulted in the changes shown here, where players are measured by an independent entity every spring, appears unlikely. It’s possible there’s a tech-based solution that can be facilitated by Hawk-Eye, but for now, the will of each individual team to put forth accurate information about their players is what I expect will continue to drive the heights and weights we see on the internet.