In its introduction to Saberseminar 2023, Scott Powers and Vicente Iglesias attack the basic truth about pitch: the variable that best predicts pitch results is where it crosses the board. For case studies, MLB.com's David Adler's tweets about Yoshinobu Yamamoto's splitter is all about.
The batsman swung 74 times in Yoshinobu Yoshinobu's splitter this season…
38 of these swings were smelling (51%)
The other 17 are fouls
Left 19 goals in the game
These 19 are ground balls (95%)
Only 1 person in Yamamoto's splitter attacks in the air pic.twitter.com/gglr1qhyzw
– David Adler (@_dadler) April 22, 2025
If Yamamoto buried one side of the separator, he might smell it. If it's on the edge of the area, it could be a foul ball. If it grabs the plate, it starts to work. Location determines the result.
Given this truth, the pitcher directing the ball should dominate the best. But there is a catch. As Powers and Iglesias noted, this location is also the variable with the lowest predictive reliability. If you see the pitcher throwing a 98 mph fastball, you're sure he'll do it again. On the other hand, the dotted rear door slider does not guarantee the entire dotted rear door slider. Command is both the most important and reliable quality for pitchers.
No one can nail corners on every court. But the pitcher can at least minimize the difference in his position, thus finding relative reliability in command chaos. In 2025, maybe no one is more reliable than Jacob Degrom.
DeGrom's flat attacks Angle Fastball and Sill Slider (reasonably) build his reputation as a monster. Even after relaxing the gas pedal this season, DeGrom remains a darling in the eyes of the model. His overall stuff + in the 80th percentage point, for starters who pitched at least 30 innings, the depth is 89 mph. PitchingBot prefers DeGrom, ranks him in the top 10 of these pitchers. Finish Baseball prospectusSuftPro model believes that DeGrom also waved four balls, in addition to the heater and slider, his curve ball and swaps – both split it into advantages.
But things are no longer DeGrom's carry tool. His decision may be his decision to lower it, which could be a positive result of aging, and now DeGrom's excellent skills are his command.
DeGrom's incredible accuracy caught my attention while writing about Hunter Gaddis's work published on Monday. As part of my efforts to tell if Gaddis should be attributed to Slider Command (verdict: inconclusive), I created a version of Kirby Index to allow Sliders to see his landing. This metric measures the difference between release angle and release point and distiles these numbers into a single fraction that captures command capabilities. Initially, it was designed for fastballs, which tend to throw them to all parts of the strike zone. For sliders, it usually has less effect, which is usually thrown towards fewer targets. Gaddis is not a good ranking among his pitchers, but Degrom's name sits at the top and catches my attention.
Kirby Index (Slider)
Source: Baseball Savant
At least 50 sliders were thrown into the right-handed batsman.
As I wrote earlier this year, a more direct implementation of the Kirby index would be to measure the difference in actual pitch position. For this story, I calculated the standard deviation of the vertical and horizontal positions of a given pitcher slider. DeGrom once again found himself on the top of his backpack. See how far he is between the next closest pitcher:
Position change (slider)
| Player name | Horizontal Position (St Dev) | Vertical position (St Dev) | Overall (St Dev) |
|---|---|---|---|
| Jacob DeGrom | 0.525 | 0.498 | 0.724 |
| Merrill Lynch Kelly | 0.595 | 0.586 | 0.835 |
| Zach Gallen | 0.616 | 0.565 | 0.836 |
| Corbin Burnes | 0.556 | 0.671 | 0.871 |
| Jack Flaherty | 0.575 | 0.659 | 0.874 |
| Elder Bryce | 0.514 | 0.713 | 0.879 |
| Zack Littell | 0.574 | 0.719 | 0.920 |
| Luarbert Arias | 0.543 | 0.755 | 0.930 |
| Enyel de Los Santos | 0.732 | 0.619 | 0.959 |
| Dylan Lee | 0.493 | 0.827 | 0.962 |
Source: Baseball Savant
At least 50 sliders were thrown into the right-handed batsman.
Random tangents are here, but you have to appreciate the slider that Luarbert Arias refuses to throw garbage anywhere outside the strike zone.
In any case, measuring position density can only end up pointing to the pitcher filling the strike zone. The real test of command is the ability of the pitcher to achieve his/her actual goals. To do this, Driveline Baseball provides me with a sample of their proprietary missed distance data. Using internal edge tracking data, Driveline measures the distance from the expected target to the actual position of the pitch.
Not surprisingly – DeGrom's slider Miss Miss distance ranks first among all pitchers. The average league distance for the slider is about 12.5 inches; this year, Degrom's target has been reduced by 9 inches, with nearly three standard deviations below average. Regardless of whether you slice it, DeGrom directs his slider like no one else in the sport.
The result is impeccable. So far, DeGrom's slider returns a run-for-mode value of -3.2 per 100 pitches, which is the best score for any slider thrown by the starter. Not only did he get a bunch of swings and missed opportunities—a 38.1% WIF rate required at the time of writing, but he also caught a lot of so-called strikes. When the batsmen do make it work, they do a lot of work on it. The average launch angle on the court is only 2°; Xwoba is a gentle .227.
The harmless result on the ball is a function of the DeGrom target. For the right-handed batsman, he aimed at the classic low corner and broke the plate. Note that the bimodal distribution on the heat map – he will throw a large number of sliders in the strike area and then another cluster below the area where the chase is generated.
These intents can be seen in the filtered heat map cluster. When DeGrom casts the slider to the right at the price of zero-potential count, he tends to be in that area:
In two hits, he chased the swing and missed:
For left-handed, DeGrom shows a similar bimodal distribution, but the pattern seems to be the opposite. In the early count, his aim was below the area. In the later stages, he was looking for a strike. This is a sequence of track and field rookie Nick Kurtz, which has four sliders, giving people a way. On 1-0 and 2-0, DeGrom tried to bait chase, but the big lefties were resisted.
Down 3-0, DeGrom fired the intermediate heater in the auto-attract scene and then returned to the slider with a 3-1 count. Here, DeGrom dials with his robotic accuracy, inserting the lower edge of the strike area to fill the count.
At 3-2, he went there again. Kurtz picked it up and paid the price. Although the superimposed strike zone on the broadcast says that the pitch is low, my feeling is that he is worthy of calling. If he always lands on the court within the intended range of his target, you just need to hand it over to him.
DeGrom is more than just drawing with a slider. I calculated the Kirby index of the four-slit fastball thrown to Righties in 2025; incredibly, he's also on that list.
Kirby Index (Fastball)
Source: Baseball Savant
At least 50 fastballs were thrown to the right-handed batsman.
While it is thought that DeGrom can be as good as it has dropped two tickings from the fastball, that is not the case. There is no improvement elsewhere, and what is lost will bring him back to Earth. But Degrom is far from stagnant. In 2019, his last major league season was the most important stage of his career—his fastball commands were below average. Six years later, it is hard to say that his order was only 80 years. As long as the elbow cooperates, it will help him resist gravity.
