Archive file · Specimen No. 06
It leaves the hand like the fastball, then sinks and runs like a splitter.
Open this like an archive drawer: grip first, source attached, shape in words, no invented spin or movement numbers. The file exists so the hold can keep moving forward.
Holds flat · arm-side run
It holds the four-seam line for most of the way, then drops late and runs to the throwing-arm side — a sudden, heavy dive off a fastball look. Down and arm-side, arriving where the four-seam never does.
ShapeOfficial dataA light two-seam split: the index and middle fingers split wide across a two-seam orientation with the ball held shallow, not wedged deep like a traditional splitter. Skenes adds index-finger pressure for the arm-side tail.
01 / At the grip bench
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Splinker / Reference model
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Hand
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Grip geometry is schematic. Skenes shows a clearly split grip on a two-seam orientation; the index-finger-pressure detail is reporter paraphrase, not a verbatim quote.
01 / Hold
A light two-seam split: the index and middle fingers split wide across a two-seam orientation with the ball held shallow, not wedged deep like a traditional splitter. Skenes adds index-finger pressure for the arm-side tail.
Grip mechanics are reporter paraphrase (MLB.com and Yahoo Sports on Skenes demonstrating it), not the pitcher's verbatim words.
Throw it like the fastball. The light split and a little index pressure add the dive.
A light two-seam split: the index and middle fingers split wide across a two-seam orientation with the ball held shallow, not wedged deep like a traditional splitter. Skenes adds index-finger pressure for the arm-side tail.
Grip mechanics are reporter paraphrase (MLB.com and Yahoo Sports on Skenes demonstrating it), not the pitcher's verbatim words.
Skenes has said the grip itself did not change when the modern, sharper version emerged; his release and the feel at release changed, which he stumbled onto on one random throw and then repeated.
Paraphrased from Skenes' FOX Sports account; his direct quote is in the chapter's voice.
Duran reached his version by widening a sinker grip; the pitch surfaced by accident in a 2018 bullpen, then he kept it. Both arms hold it to look like the four-seam out of the hand.
From MLB.com's feature on Duran, who first popularized the pitch.
Release Room
Grip shape only matters if the release makes sense. Read pressure, thumb support, and ball depth before you read the pitch shape.
A light two-seam split, the ball held shallow, not wedged deep between the fingers.
Adds the arm-side tail with extra pressure
Fastball arm and full intent; the light split and index pressure add the sink and tail.
Thrown with fastball arm speed and full intent. The light, low-spin split lets the ball drop and run to the arm side, and because it leaves the hand on nearly the same path as the four-seam, hitters cannot separate the riding fastball from the diving hybrid until it falls.
Paraphrased from MLB.com's coverage of Skenes' debut splinker.
Movement
The read is shape, not a gauge. The spin words explain why it moves that way, and every prose claim still carries its source.
Shape
Holds flat · arm-side run
It holds the four-seam line for most of the way, then drops late and runs to the throwing-arm side — a sudden, heavy dive off a fastball look. Down and arm-side, arriving where the four-seam never does.
Spin words
A low-spin, sinker-like axis with arm-side tilt, but the flight path stays close to the four-seam's out of the hand, so the two look alike before the splinker dives.
Craft read
It tunnels off the four-seam, leaving the hand on nearly the same path at fastball speed. Then the light split lets it dive down and toward the throwing arm, so the hitter has to guess which fastball is coming.
The one teaching sentence
It is a second fastball shape: fastball arm speed off the same slot and release as the four-seam, then a late dive and arm-side run the four-seam never makes. The hitter has to choose between the riding pitch and the diving one out of the same hand.
Master Files
The few arms throwing it: the one who popularized it, the one who made it famous, and the closers chasing it. The visual is our own seam schematic. What sets each version apart is in the read, not a gauge.
Made the pitch famous. Discovered it by accident playing catch after the 2023 College World Series, then turned it into one of the most valuable pitches in baseball.
The definitive modern splinker: a fastball look that holds the four-seam line, then dives arm-side and down so late hitters keep waving over it. It plays like a second fastball with a trapdoor.
The arm who first popularized the splinker, discovering it in a 2018 bullpen after widening a sinker grip. The power version of the pitch.
The power version: splitter-grade arm-side dive carried with fastball intent, so the dive lands without the usual soft-pitch tell.
Added the splinker to a triple-digit fastball and a wipeout slider, unveiling it in a May 2024 game with extra horizontal ride.
Bolted onto an elite power arsenal — his version leans hard to extra arm-side run, a third look off the same upper-tier heat and the wipeout slider.
The colophon
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108 double stitches, 216 individual · seam-informed schematic · as of the dates above
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Another fastball in the collection
Index and middle fingers laid across the seams at the open end of the horseshoe, the seam that faces away from the body. Thumb underneath on the leather. Held loose toward the fingertips.
Paraphrased from the cited reference, not quoted. Corroborated by Wikipedia (Fastball) and eFastball.
The person behind the pitch
Others in the fastball
Tier 03 / Field Notes
Every pitcher fiddles. A thumb creeps lower, a seam catches more leather, a cue from a coach suddenly makes the pitch move. Pitch Atlas files those experiments as specimens with context, so the small discoveries stop disappearing into group chats and comment sections.
How notes rank
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Source tier and evidence. A coach-observed note with a link outranks an unverified hunch with none.
How many other pitchers independently tried the same tweak. Real replication, not passive clicks.
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How close a note is to your level, slot, and pace context. Computed in your session, never stored.
Considered practice: a real sample size behind the claim, not one good bullpen.
The vocabulary
Your bullpen card
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