Every baseball game every night includes pitch sorcery like nothing we have seen before. The average major league pitcher throws harder than ever (an average of 94.0 mph on two- and four-seam fastballs, matching the record of last year) but throws fewer fastballs than ever. The rate of fastballs is down to 47.3%. Just 10 years ago a hitter could expect to see 56.8% fastballs.
All those lost fastballs have been replaced with a confounding web of lab-grown pitches that dart every which way. Shaping and sequencing, not velocity, is the coin of the realm. The typical starter throws three versions of a fastball that cut, run and ride, and two or three off-speed pitches that sink or veer or do both.
Thirty-three starting pitchers throw at least five pitches at least 10% of the time, an astounding galaxy of permutations for a hitter to try to suss out what is coming out of a pitcher’s hand. Zack Wheeler of the Phillies, the grand master of the pitch-shaping evolution, throws six pitches between 10% and 41%.
“Ten percent is important,” says Tigers manager A.J. Hinch, “because that gets a pitch on the [scouting] report.”
It’s the threshold in which a pitch must be honored. And hitters have never had to honor so many pitches that move so fast in so many directions from so many different pitchers. MLB teams used more pitchers to play the first two months this year (630) than they did to cover the entire 2005 season (606).
Ten years ago, Dallas Keuchel won a Cy Young Award throwing 62% fastballs (sinkers and four-seamers) that averaged 89.9 mph. He did not reach today’s average velocity with any one of his 3,492 pitches. This wasn’t Old Hoss Radbourn. This was just a decade ago—but it is now ancient history when it comes to how pitching is crafted.
It should not be a surprise, then, that one-third of the way through this baseball season slugging has fallen to the lowest in a decade (.394). Runs and home runs are down slightly, though better conditions through the summer months could boost them.
This is a robust pitching environment, which makes it seem all the odder that pitchers and catchers are complaining about a shrinking strike zone this year.
Are they right? Is the strike zone really smaller? Or is it confirmation bias? And if it is smaller, is that good or bad for the game?
First, the back story. MLB tested the ABS challenge system it uses in the minor leagues in major league spring training games this year. A batter, pitcher or catcher could challenge an umpire’s ball/strike call by calling for the laser-guided evaluation of the pitch, like the HawkEye system used to call lines in tennis.
By most every indication, the experiment went well, especially with fans. But there was an underlying problem in this timeless humans vs. machines showdown. Umpires for years were graded on an internal system that gives them a buffer zone of two inches, nearly the width of a baseball. A ball two inches off the plate called a strike counted as an accurate call on the umpire’s report. The ABS system has a median error of less than one-fifth of an inch.
To bring umpire zones more in line with machine zones—and anticipating a 2026 adoption of the ABS system—MLB this year reduced the size of the buffer zone in its umpire grading system to three-quarters of an inch. This season becomes a training ground for the intractability of robots.
The ABS Challenge System is here!
— FOX Sports: MLB (@MLBONFOX) February 20, 2025
Cody Poteet is the first player to challenge a call, and he won it!
(via @WatchMarquee)pic.twitter.com/0a4YDHtV3C
What catchers and pitchers notice now is that edge pitches, especially on the top and bottom rails of the strike zone, are more likely to be called balls rather than strikes.
It turns out it’s not just confirmation bias. They are correct. But how often?
Umpires are fabulous at what they do, especially given the modern sorcery of pitching. They get calls right more often than they did 10 years ago. The younger umpires, who grew up with HawkEye systems and tend not to have the injuries or eroded physical dexterity of older umpires, are especially keen. According to UmpireScorecards.com, an unofficial accounting of pitch calling, the five most accurate umpires are all under 45: Edwin Jimenez, 32, Derek Thomas, 34, Mark Ripperger, 44, Junior Valentine, 37, and Dan Merzel, 37.
A home plate umpire makes an average of 145 ball/strike calls each game, according to pitch-tracking data from StatCast. Most of those calls, 98, will be on pitches out of the zone. Of those 98, only 4.95% of the time the umpire will call a strike. That’s about five pitches per game an umpire calls a strike on a pitch out of the zone. But given an allowable buffer zone and margin of error in recording pitches, it’s probably three or four.
For argument’s sake, let’s stick with five calls per game this year in which the umpire “gives” the pitcher a strike. How does that compare to last year? Through the same date last year, when the umpires still had their baseball-wide buffer zone, umpires called strikes on pitches out of the zone 6.17% of the time.
With the shadow of the coming ABS, called strikes on pitches out of the zone have dropped from 6.17% last year to 4.95% this year. That means this year pitchers are getting an average of 1.195 fewer edge pitches called a strike.
One strike per game. That’s it.
That’s not nothing, but it’s hardly worth getting into a lather about.
Let’s go back further. Ten years ago, when umpires tended to have “personal” strike zones, umpires gave the pitcher a strike on 9.8% of pitches out of the zone. (Much to the delight of finesse pitchers such as Keuchel.) That’s twice the rate we see today. Today’s pitchers may get 1.195 fewer edge calls going their way as compared to last year, but they get 4.75 fewer edge calls per game than they did 10 years ago. That is significant. Umpires are better, and technology has helped them get better.
Here is the Statcast data as compiled through May 25 of this year, a year ago and a decade ago:
MLB Through May 25
What effect is one fewer edge strike having on the game today? Very little. The strikeout rate is down, walks are up and the percentage of strikes that are looking is up, though that is likely due to the sequencing and shaping emphasis.
MLB Pitching Rates
The ABS system is not a done deal yet for the 2026 MLB season. The system still needs fine-tuning among the lab work that is the minor leagues, and players and owners will need to agree on how it is implemented, especially with how the strike zone is defined. The ABS zone used in Triple A, for instance, is smaller than the current MLB called strike zone.
“I went down to Toledo last week on rehab,” says Tigers catcher Jake Rogers. “It’s a lot smaller. There was one pitch at the top of the zone I caught that was called a ball. I went back and looked at it and against the major league strike zone. The entire baseball was in the strike zone. It’s different, which is why there is so much offense there.”
The International League ERA was 4.92 at the start of this week. The batting average was .251.
“The biggest thing is not the technology but defining what the strike zone is,” says Tigers ace pitcher Tarik Skubal. “Just about everything lately added to the game has favored the offensive side. I get it. Fans want to see home runs. They want to see action. The home fans want to see strikeouts. What nobody wants to see are more walks. You have to be careful that one of the unintended consequences is not more walks.”
Pitching is so good that MLB does need a thumb on the scale on the offensive side. The quickest fix would be to lower the top of the strike zone while calling the exact width of the plate, 17 inches. On pitches inside the top of the strike zone by just three inches—about the size of a baseball across the top of the zone—hitters this year are batting .193. Take away just that sliver across the top and force pitchers to work lower and you will see more offense. But to Skubal’s point, maybe you also get more walks, slowing a game that since the pitch timer is finding a pleasant rhythm and better balance between offense and defense.
The ABS challenge system is coming and the (slightly) smaller strike zone this year is a logical transition toward it. The system doubles down on the original intent of the challenge system on the bases: let no game be decided by an egregious call obvious to all. Get the biggest calls right without sweating every single one. Get the fans engaged. (As in tennis, fans dig watching the animation play out and don’t have to wait long to get it.) Get more strategy in the game. Strategy?
“I think it’s one more piece of the skill set for catchers,” Rogers says. “You have to know when to challenge. You have to know the situation and you have to know the strike zone in the blink of an eye. There is a skill to that. And like any skill, some will be better than others.”
The next time you watch a baseball game you can moan about the “smaller” strike zone, or you can marvel at the aerial wizardry that is happening between the pitching rubber and the plate, where baseballs zig and zag like hobby drones. Pitching has never been this hard to solve, and yet hitters do solve it often enough to keep the game in balance. The strikeout rate this year (8.56 per nine innings) somehow is at its lowest level since 2017.
April 22 in Detroit was just another night in the steady stream of nights when the game is played at such a high level we have grown accustomed to the skill. Nick Pivetta of the Padres, a re-invented pitcher at 32 years old with his fourth organization, and Jack Flaherty of the Tigers, who at 29 no longer resembles the kid who in the best of his younger years threw 58% fastballs, locked in a pitchers’ duel. Pivetta spun 38% breaking balls. Flaherty spun them 54% of the time. Each was followed by two relievers, including Padres righthander Robert Suarez, who threw 99 mph, and Tigers righthander Chase Lee, a sidearmer who threw Frisbee sweepers. The hitters managed nine hits against 19 strikeouts. The Padres won, 2–0. And behind the plate, umpire Junior Valentine made 127 calls, all but one of them correct.
More MLB on Sports Illustrated
This article was originally published on www.si.com as Yes, MLB’s Strike Zone Is Shrinking. But Baseball Will Be Better for It.
