Maybe. A lower arm slot can turn an ordinary fastball into a swing-and-miss pitch, but it can also cost velocity, and it depends on a hand position many pitchers do not have. The right answer depends on your body and your current fastball, so treat a slot change as an experiment you can measure and reverse.
The league is going lower
Driveline's Travis Sawchik compared the same pitchers year over year from 2016 to 2025 and found that MLB pitchers lowered their slots in eight of those ten seasons. Releases are now about two inches lower than in 2016, and average arm angle has fallen about 1.4 degrees since 2020 [1].
The poster child is Zack Wheeler. His four-seam arm angle dropped from 38.9 degrees in 2021 to 31.8 degrees in 2023 [1][2], and he built one of the most valuable fastballs in baseball. Bryan Woo of the Mariners throws his four-seamer about half the time from a low release and very flat approach angle; Baseball Savant credits it with a +21 run value in 2025 [1][2].
Why a lower slot works
Hitters build their swing around an expected path. A fastball released lower arrives on a flatter vertical approach angle, so it stays above the path a hitter expects. Hitters swing under it, even when the pitch has only average induced vertical break [1]. That is why a fastball with modest ride from a low slot can play better than the same ride from a high slot.
A lower slot also opens up more pitch shapes. It makes sinkers, cutters and sweepers easier to reach and gives more access to seam-shifted effects, which is part of why teams like it [1]. Seam-shifted wake is a real aerodynamic force: lab work by Smith and Smith showed that seam orientation alone can push a pitch sideways [3].
The catch: what a lower slot can cost
- Velocity. Pitchers who lowered their slot lost about 0.15 mph on average from one season to the next [1]. That average hides big individual losses.
- Backspin. Keeping true backspin from a lower slot takes enough radial deviation, a wrist mobility trait. Driveline reports Joe Ryan's four-seamer at about 97% active spin and Woo's at about 91%. A pitcher who cannot keep efficient spin from the lower slot can still use a cutter to keep some lift [1].
- Fit. Paul Skenes lowered his slot in spring training 2025 and went back to his 2024 slot for the season [1].
- Ride. Lower slots tend to trade vertical break for horizontal run. If your fastball's value comes from elite ride, dropping your slot may give away your best trait.
Tread's Ben Brewster tells a cautionary story about an undersized lefty with a 94 to 96 mph riding fastball whose organization converted him to a sweeper and changeup pitcher. His slot and ride dropped, his velocity fell to 88 to 92 mph, and he was out of baseball within a couple of years [4]. It is an anecdote with no names attached, but it shows the downside of a slot change made for the arsenal instead of the athlete.
Is a lower arm slot safer?
Do not change your slot for health reasons based on current evidence. One lab study of 66 elite college pitchers found arm slot was related to elbow and shoulder torque, with less elbow varus torque in the lower-slot group [5]. It was a single cross-sectional dataset, and the abstract's description of the direction is internally inconsistent. Driveline's own look at MLB data found a weak pattern the other way, which likely reflects selection bias [1]. The honest summary: the health effect of slot is unresolved.
Measure the trade-off
Log release traits alongside the pitch
Pitch AI's Pitch Lab logs velo, release height and extension, the traits pro teams prize, along with IVB, spin and axis for every pitch. Log both versions of your fastball and compare them on the movement chart before you commit to a new slot.
Kyle Harrison went up and got better
If you need a reason to avoid treating "lower is better" as a law, look at Kyle Harrison. After joining Milwaukee, he moved across the rubber, and his fastball arm angle went up [6][7]. The verified Statcast numbers [2]:
| Four-seam fastball | 2024 (SF) | 2026 (MIL) |
|---|---|---|
| Arm angle | 26.1° | 33.0° |
| Velocity | 92.6 mph | 94.8 mph |
| Induced vertical break | 10.8 in | 14.7 in |
| Release side (toward first base) | 1.86 ft | 2.74 ft |
His fastball gained almost four inches of ride, and his slurve became one of his best pitches: its expected wOBA fell from .356 in 2025 to .249 over the full 2026 season [2]. Several things changed at once, including rubber position, slot, usage and a new changeup grip, so no single change gets all the credit [7]. The lesson stands anyway: the best slot is the one that fits the pitcher.
Your slot sets your pitch menu
The deeper point from Driveline's Saberseminar 2025 research is that slot and hand action work together. Hold the hand action constant and change the slot, and the pitch changes: the same manipulation gives Tyler Rogers a rising slider from his submarine slot and gives Justin Verlander a curveball [8][9]. Driveline's coaches also say the hard "vertical slider" suits higher slots with a slight supination bias, while lower slots drift toward cutter and gyro shapes [10].
So the better question is: which slot fits my body, and which pitches does that slot reach easily? Our guide to what pitches to throw from each arm slot maps this out, and how to throw a four-seam fastball covers spin and ride.
How to test an arm slot change
A slot test does not need weeks. A Driveline trainer describes ruling out a lower slot in about six throws when it clearly does not feel right [1]. A simple protocol:
- Do it in the offseason. Slot changes are big changes; keep them out of the competitive season.
- Film both versions. Use the same camera angle so you can see whether the trunk tilt or the arm changed. Our guide to checking mechanics on video covers setup.
- Run a blind velocity split. Alternate your normal slot and the new one for five or six throws each at equal effort while a partner hides the radar readings [4].
- Stop if you lose real velocity. A Driveline trainer's rule of thumb: a drop that costs two miles an hour usually is not worth it; one that costs nothing and feels good might be [1].
If the lower slot holds velocity and feels natural, give it a few weeks of catch play and bullpens before judging the fastball shape. If you have a tracking device, compare release height, vertical break and spin on the same device.
What to do this week
- Film your fastball from behind and from the side, and note your current slot.
- If a coach has suggested a lower slot, run the blind split test in your next throwing session.
- Write down which pitches come easily from your current slot. That list is your starting menu.
Next in this series: is the sweeper dead? And for the full Harrison story, see how Ben Brown and Kyle Harrison transformed their pitches.
Frequently asked questions
Does a lower arm slot increase velocity?
Usually not. Driveline found MLB pitchers who lowered their slot lost about 0.15 mph on average from one season to the next. Some pitchers lose much more, which is why any slot change should be tested with a radar gun before it is adopted.
Is a lower arm slot safer for the elbow?
The evidence is limited. One lab study of elite college pitchers linked arm slot to elbow torque, with less torque in its lower-slot group, but it was a single cross-sectional dataset. Driveline found a weak opposite pattern in MLB workload data. Neither supports changing your slot for health reasons alone.
Why does a low arm slot make a fastball play better?
A lower release makes the fastball arrive at the plate on a flatter vertical approach angle. Hitters expect a steeper path, so they tend to swing under it, even when the pitch has only average ride.
How do I know which arm slot is right for me?
Your natural slot and hand position decide which pitch shapes you can reach. Test small changes for feel and velocity in a handful of throws, keep what holds velocity, and build your arsenal around the slot that fits your body.
Build around your slot
Find the arsenal your release reaches
Pitch AI's Pitch Lab logs velo, release height and extension, the traits pro teams prize, plots your arsenal, and ranks what to develop next. AI Video Review gives cues and top fixes from your own throwing video, so you can see what a slot experiment did to your delivery.
References
- Sawchik T (2026). Pitchers are going low, and for good reason. But it's not for everyone. Driveline Baseball, March 12, 2026. https://www.drivelinebaseball.com/2026/03/pitchers-are-going-low-and-for-good-reason-but-its-not-for-everyone/
- Baseball Savant, MLB Advanced Media. Statcast pitch-level search and Pitch Arsenal Stats leaderboards, 2021 to 2026 seasons; retrieved and summarized by Pitch AI on October 14, 2026. https://baseballsavant.mlb.com
- Smith AW, Smith BL (2021). Using baseball seams to alter a pitch direction: the seam shifted wake. Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology. doi:10.1177/1754337120961609 https://doi.org/10.1177/1754337120961609
- Tread Athletics (Brewster B) (2026). Throw Harder By Changing Your Pitching Mechanics [The Right Way]. YouTube, September 24, 2026. https://youtu.be/_EilR25ydwY
- Dong M, Li M, Qu Q, Kim Y, Kim S (2025). Arm slot angles affect elbow and shoulder joint torque in elite college pitchers. Sports Biomechanics, 24(8), 2166-2183. doi:10.1080/14763141.2024.2431927 https://doi.org/10.1080/14763141.2024.2431927
- McKibbin J (2026). How Kyle Harrison's Move Across the Rubber Has Finally Given Him a Breaking Ball Worthy of His Fastball. Brewer Fanatic, April 30, 2026. https://brewerfanatic.com/news-rumors/milwaukee-brewers/how-kyle-harrisons-move-across-the-rubber-has-finally-given-him-a-breaking-ball-worthy-of-his-fastball-r4466/
- Brozdowski L (2026). The Brewers Pitching Lab Must Be Stopped. YouTube, June 29, 2026. https://youtu.be/Y9qkukpL3A4
- Hejka J, Lambert J, Ramilo M; Driveline Baseball (2025). Projecting Pitch Design, Saberseminar 2025 presentation. YouTube, December 31, 2025. https://youtu.be/HeBvjYrU_vk
- Driveline Baseball (2026). The Evolution of Pitch Design, Saberseminar 2025 (R&D Podcast Ep. 111). YouTube, January 19, 2026. https://youtu.be/2fjpL_BraVU
- Driveline Baseball (Lambert J, White C) (2026). What's the Next Sweeper? YouTube podcast, July 28, 2026. https://youtu.be/QPzFR4GNxdk