Automatic strike zones have made pitching in the minors a whole new ballgame
In the olden days before fine grain data was available on all pitchers at all times, walk rate was one of the more reliable measures for projecting how a hurler was likely to perform at the next level.
The ability to consistently throw strikes is a necessary precondition for major league success, and while it would be fair to expect a slight uptick in the frequency of walks after a promotion, there wouldn’t often be a significant change.
What happens to player evaluation, though, when the lower level is no longer playing by the same rules?
Triple-A is utilizing an automated balls and strikes (ABS) system for all games in 2023 as part of MLB’s process for eventually introducing the technology to the big leagues. For half the six-game week, balls and strikes are determined purely by the TrackMan radar system. For the other three games, a human umpire calls balls and strikes, but the batter, pitcher and catcher can challenge up to three pitches per game, per team, with outcomes determined by the radar.
The automatic zone was used at lower levels in 2022, and as part of the league’s tweaks, it’s now significantly smaller. Baseball America reported in May that the strike zone is now 17 inches wide (the exact width of home plate) rather than 19 inches, and begins vertically at 51% of a batter’s height, as calculated by TrackMan. In 2022, that measurement was 56% of a batter’s height.
That means the strike zone for every hitter only goes as high up, roughly, as their waist. Strikes at the letters no longer exist. Pitchers who feel they need to work in the top of the zone are struggling to balance throwing competitive pitches with issuing free passes.
Or, as Dakota Hudson wryly put it following his Sunday start, “considering the top (of the zone) at Memphis is middle middle, it’s a different game.”
Hudson struggled to a 7.31 earned run average at Memphis this year, walking 3.2 hitters per nine innings. In the majors, he’s cut that number down to 2.9, and his ERA with it to 4.15. Last season, those numbers were flipped; he walked half a batter more per nine in the big leagues than in Triple-A.
He’s not alone.
Zack Thompson turned in an intolerable 10.2 walks-per-9 innings ratio in the minor leagues this year, paired with a respectable 3.9 in the majors. That sort of discrepancy can’t come close to being entirely explained by the size and shape of the strike zone, but for a pitcher struggling with his confidence and his place in the organization upon his demotion, it certainly couldn’t have helped.
“Not to make excuses,” Thompson said, echoing the preface of others, “but as more of a vertical guy, not being able to throw the heater to the top of the zone down there affects the way you cover the curveball. That’s where I started throwing the slider at the top of the zone more.”
Hudson doesn’t rely on a sweeping curve ball in the same way Thompson does, but their problems are similar. His best pitch – his most valuable skill – has always been a sinker that should have biting downward action in order to induce ground balls. That pitch has to be thrown at the bottom of the zone to work, so to keep hitters off balance, he has to be able to cover the top.
Hudson’s four-seam fastball is simply not a good enough pitch to sneak past upper level hitters when it’s coming in belt high. So if batters can feel dialed in on the bottom of the zone but don’t have to worry about being challenged at the top, they can get their hands into a dangerous area and do damage.
Or, they draw walks.
“Yeah, potentially,” manager Oliver Marmol said when asked if the changes at Triple-A had posed challenges for some of his recently recalled pitchers. “Strikeouts and walks are usually pretty predictive, right?”
If nothing else, that uncertainty provides a little context to the decision to lean heavily on Hudson and Thompson down the stretch – and, to date, to see results which have validated those decisions. Hudson still profiles as largely the same pitcher he’s always been, which is to say he’s reliant on batted ball luck and finds himself in a lot of trouble when walks are coupled with balls in play which sneak through.
Thompson, though, has cut his walks plus hits per innings rate by nearly a full base runner in St. Louis as compared to the Memphis, is striking out a full extra hitter per nine innings in the big leagues, and has improved his strikeout-to-walk ratio by a factor of three simply by virtue of being promoted.
Here, he can throw a heavy fastball and a tight slider up closer to the letters where hitters have to respect it, and then mix in his plunging curveball. Pitching is working in, out, up, and down. If half of the equation changes drastically, so too does success.
“Each pitch can compliment another,” Hudson said. “Anything and everything at all times, I think that’s a good way to just get out there.”
Good for the pitchers, at least.
