I've been writing about the strike zone for several years and if so far my work has a general theme, then what the referee is doing is excellent. When Major League Baseball launched the Pitchf/X in 2008, the referee received 84.1% of the batting calls based on the Statcast strike zone. In the following years, while more and more things and the revolution of pitch frames made their work harder, referees were better. Accuracy broke 92% in 2021 and entered 93% over the next two seasons. The annual improvement trend has finally changed in 2024.
As I wrote yesterday, last season marked the first time the referees have gotten worse than better. This is fun enough in itself, but the game changes when it's time to doubt whether they'll be as good as possible. During the offseason, a new Labor agreement includes changes to the way the league evaluates referees. The grading became tighter, reducing the buffer around the edge of the strike zone from two inches to three quarters of an inch. The strike zone is the same, but the referee is even more nervous. Let's dig deeper into the numbers and see how this season looks different so far. Here is a chart showing the overall accuracy of each season in the pitch tracking era.
The yellow line shows overall accuracy and can be restored to its original state starting in 2024. Even though this is the beginning of the season, the referees are at least accurate when they are still better than last year. Accuracy has dropped from 92.81% in 2023 to 92.53% in 2024, and now it has returned to 92.63%. Actually, it's fairer if you only look at the March and April statistics, as the referees will be worse early in the season – you'll find that the referees are just the best opening month ever. They correctly call 82% of the pitch in the shadow area.
The fact that accuracy has recovered ticking is not necessarily the fact that I am interested in. I suspect this could happen anyway. Referees have been getting better and better every season for decades, and a very bad season doesn't mean they've completed a complete improvement. What I'm interested in is that the difference between the red and blue lines in the picture above is so big. The following image shows a clearer effect, as it shows the pitch in the shadowed area within only one baseball width at the edge of a baseball area where the judgement's judgment is indeed tested.
All the time, on the right side of the picture, those red and blue lines have been the true story here. Yes, the referees this season are a little more accurate, but their improvements have a very clear pattern. They performed much better in judging courts outside the strike zone and were even worse in judging courts inside the strike zone. In other words, they're always calling for more balls. This will make you more accurate because naturally, players tend to swing on more courts in the area and make more pitches outside of them. The blue line shows that the field performance in the area has dropped to its lowest level since 2016. This is 10 years of progress! This season, 42.7% of ball calls in the Shadow Zone ended up in a strike. This is the lowest rate ever recorded. This is what the line graph looks like.
Look at how the shots are taken down this season. Now considering that 44.9% of these stadiums have actually reached the strike zone so far, the highest pace in 10 years. This is the same graph, but also includes the area rate.
The regional rate does seem to have nothing to do with the so-called hit rate, especially this year. That's why pitchers and catchers keep telling sports The strike zone is shrinking. Yes, the accuracy has improved, but it has been greatly improved. Not only that, the giant's complaints to them are more specific, telling San Francisco Chronicles In particular, the high strike has disappeared. To check it out, I extracted the exact data on three specific parts of the shadow area. Let's start with the side of the plate. Attack areas 14 and 16 cover the shadowed area on each side of the board – 14 is located inside the right-handed batsman, 16 is on the outside – but the pitch is excluded in the top and bottom shadow areas. We will arrive at the corner later. The trend here has been going on for a long time.
The referees are steadily getting better and better on the side of the plate, and this improvement is usually on the court outside the strike zone. They are getting better at identifying balls, but this season, this improvement does come at the expense of their accuracy within the region. They are still more accurate overall, but they lack more strikes than ever before. This is another way to view these trends. The following figure shows the average horizontal position of each ball or in both areas called a hit. The grey area shows the actual width of the plate.
As you can see, the so-called strike has been getting closer and closer to the actual edge of the plate, while the so-called ball has gone further and further away. The average of the edge of the board is called a blow, which is actually at the edge of the board. However, all four lines outline some feet in the approaching plate this season. The area is simply closer.
Now, let's look at the bottom of the strike zone. As I wrote before, over the years, referees have become more accurate at the bottom of the area. The figure below shows the attack area 18, at the bottom of the area in the middle of the board. We ignore the corner again because we want to know where the real bottom of the area is without letting the side of the board affect it.
The bottom of the strike zone has been greatly lowered over the years, with the receivers in the league taking a knee pose to win more strikes there. From 2009 to 2020, the average strike height at the bottom of the area dropped by 1.92 inches. But, ever since, this average has been ticking. This season, it is 0.6 inches taller than in 2020. Still, the effect has not been as dramatic as the edge of the sector so far this season, where referees are actually getting worse and worse in identifying strikes.
Finally, let's look at the top of the area where the Giant highlights the problem area. The image below shows attack area 12, with the top of the area in the middle of the plate, which certainly looks like there is a little bit in San Francisco. Not only are the referees calling more closely there, but they have always called it so tight that they actually have less accuracy overall.
There is a reason that this picture doesn't look like the others. The straight lines of others tell a neat story. On the side, referees are always good at identifying strikes, and over the years they have been better at identifying the balls, essentially because they have been better at finding the edges of the board. At the bottom of the area, referees are always good at identifying balls, but they gradually improve in identifying strikes and lowering the area.
The top of the strike zone is blurry than the sides and bottom. Not only did the referee glance at the plates to visually guide them, but the top of the area varies even more by batter than the bottom. Additionally, since the referee must take into account the batsman's posture, the top of the rulebook area is different from the top of the Statcast area, but the Statcast doesn't take into account. All of this is to say that the top of the area is where the referee has to make the most judgment. This season, this is the most inaccurate place ever.
Below is a heat map where I'm trying to show the possibility that the pitch in the shadowed area is called a strike. This includes each shaded area starting in March and April 2025. The darker the red, the more likely it is to be called a strike.
On the sides and bottom of the area, it was obvious that things had tightened. Less spreads around the edges and stronger red. But at the top is a completely different story. If anything, it will be more scattered. The light red part on the top reaches higher. The deeper part is not that dark, and it pushes lower. The referees there are not very consistent. They called strikes at the top of the area and higher strikes. It's just messy. However, if you break things through the attack area of Statcast, the overall situation is not clear. The following figure shows the change in strike rates from 2024 to 2025. The blue area and negative numbers mean the referee is more likely to call the ball. The red segment and positive numbers mean the referee is more likely to cause a strike, but you don't really need to worry about that. There are no red segments.
There is no red on this chart. The biggest gain comes from the bottom of the heart area, but they are at a tenth of a percentage point. This is a very blue chart with the darkest corners. The area will certainly shrink, and all catchers and pitchers think that the meaning of losing the strike is a real point of view. As Patrick Dubuque Baseball prospectusthe league's walking rate has increased.
In a sense, it is hard to imagine that such adjustments are done in any other way. I keep thinking about the first image I showed you as I tried to wrap my head around the changes I have seen so far.
I've been making a version of this picture for years and I think it has a lot to say about the actual situation of the referee. It is much easier to identify the ball than to identify the strike, and no matter how precise the referee gets, it is true. The area has always been an oval thing, and although the corners have tightened greatly over time, they never become completely crispy. It is predictable that tightening it this season will result in more balls, and in some way, bias masks the fact that referees are the most accurate start we've ever seen.
