How to throw a two-seam fastball or sinker

The two-seam fastball and the sinker are fastballs built to move toward the pitcher's arm side and finish lower than a four-seamer. For a right-handed pitcher, that means run in on a right-handed hitter's hands and sink under the barrel. Their job is different from a riding four-seamer: instead of making hitters swing under the ball at the top of the zone, they move off the barrel low in the zone, which tends to produce weak contact and ground balls.

The names overlap. Statcast groups two-seamers under its sinker label, and coaches use the terms loosely. In everyday use, "two-seam" usually describes a grip, while "sinker" describes the result: a fastball with lots of arm-side run and less ride. Premier Pitching's two-seam guide notes that the two pitches share similar grips and are separated by subtle grip and pressure adjustments. This guide treats them as one family.

Why the sinker moves: spin plus seams

A four-seamer moves mostly because of spin. A sinker gets help from the seams as well. Research led by Barton Smith's lab at Utah State University described the seam-shifted wake: when the seams sit in certain positions as the ball flies, they make air separate earlier on one side of the ball than the other, which creates a force that spin alone does not explain. Driveline's analysis of 2020 MLB data found the effect was most pronounced on sinkers, and that the average sinker gained more than 3 inches of run and nearly 4 inches of depth from non-Magnus effects.

The practical takeaway is that small changes in where your fingers sit on the seams can change sinker movement more than you would expect from the grip alone. Driveline's grip guide makes the same point: minor adjustments on the seam and a slight tilt can significantly change two-seam movement.

Two-seam and sinker grip, step by step

1. Find the narrow seams. Turn the ball so the two seams run closest together. Lay your index and middle fingers along those seams, not across them.
2. Choose on-seam or one-seam. The classic two-seamer puts each finger on top of a seam. A one-seam variation puts one or both fingers on a single seam. Driveline found that 12 of the top 20 pitchers by seam-shifted-wake effect in its 2020 sample threw one-seam style sinkers.
3. Set finger spacing. Start with a normal fastball width and test closer or wider. Wider can increase run for some hands; closer can keep velocity up.
4. Thumb underneath. Place the thumb under the ball, tucked or flat, wherever it is comfortable and stable.
5. Pressure. Many pitchers feel slightly more pressure through the index finger to encourage arm-side run. Premier Pitching describes asymmetric pressure on the index finger side as a source of run.
6. Depth. Keep the ball in the fingers. A deeper grip can kill velocity, which is the last thing a fastball needs.

Release and hand action cues

Throw it like a fastball. That is the most important cue. The movement should come from grip, seam orientation, and slight hand position, not from slowing the arm or twisting the wrist. Driveline's grip guide lists cues such as "stay through it," "get over the top of it," and "roll over the ball." Cues that tend to work:

• "Slightly inside the ball." A small feel of the hand working to the outside of the ball (the thumb side) tilts the spin axis toward the arm side.
• "Pressure through the index finger." Let the index finger finish the pitch to encourage run.
• "Same arm speed, same finish." If velocity drops, the cue is probably too forced.

Slot matters. Driveline's 2026 reporting on lower arm slots notes that sinkers and sweepers benefit from lower slots. If your fastball already runs and does not ride much, a sinker may be a better primary fastball than a four-seamer. The arm slot guide walks through that decision.

Typical movement and velocity

Baseball Savant's pitch movement leaderboard for the 2026 regular season shows how sinkers compare with four-seamers among qualified right-handed pitchers (averages weighted by pitches thrown).

Among right-handers who threw both pitches, the median sinker was only 0.4 mph slower than the same pitcher's four-seamer. That is the point of a sinker: it is a real fastball. It trades roughly half of the four-seamer's ride for about twice the arm-side run, while keeping almost all of the velocity.

Common sinker mistakes

• Losing velocity. A sinker that is three or four miles per hour slower than your four-seamer is starting to play like a changeup without the deception.
• Dropping the slot to make it sink. Changing posture or arm slot for one pitch tips it to hitters and can damage the rest of the arsenal.
• A sinker that moves like your four-seamer. If the two shapes are only an inch or two apart, hitters are not facing a different pitch.
• Over-pronating early. Turning the hand over before release often makes the ball spray arm side and costs command.
• Judging by feel alone. Seam effects are hard to see. A pitch can feel great and move ordinary.

How to test and refine a sinker

Because seam effects are a big part of the pitch, measure it. A tracking device such as Rapsodo or TrackMan reports velocity, spin, IVB, and horizontal break, which tells you whether the pitch actually separates from your four-seamer. Driveline's seam-shifted wake work compared the spin axis a pitch was released with against the axis implied by its movement; a large gap between the two is a sign that seams are adding movement. A high-frame-rate slow-motion camera helps you check the seam orientation coming out of the hand.

1. Throw 8 to 10 baseline four-seamers, then 8 to 10 sinkers with your starting grip. Record averages.
2. Change one thing: on-seam versus one-seam, finger width, or index-finger pressure. Throw another block.
3. Look for separation from the four-seamer (less ride, more run), velocity within about a mile per hour, and strikes to the arm-side half of the plate.
4. Repeat the best version in a second session before committing.

How the sinker fits with other pitches

The sinker's natural partners move the other way. A slider or sweeper that starts on the same line and breaks to the glove side creates a wide horizontal window, and a cutter gives a firm glove-side contrast. A changeup can mirror the sinker's run with less speed. Many pitchers carry both a sinker and a four-seamer; Driveline's 2025 analysis found 92 of 253 qualified MLB starters threw three or more fastball types at least 5% of the time. Read why a second fastball shape can unlock an arsenal for how to decide, and see the pitch grips hub for every grip in one place.

Count new-pitch reps as real throwing workload

Learning a grip is skill work, and skill work needs volume. The way to get that volume without a spike is to plan for it. Bullpen reps of a new pitch, dry-run catch-play reps at shorter distance, and flat-ground tests all count toward your daily throwing workload, so log them the same way you log a bullpen. Add the new pitch inside your existing bullpen count at first (swap some fastballs for it) instead of stacking extra throws on top, then let the total grow as your chronic workload grows. That keeps your acute:chronic workload ratio steady while the new skill builds. A sinker test fits naturally inside a normal bullpen: swap half of the fastballs for sinkers rather than adding a separate block.

Readiness matters too. A grip block is a good fit for a day when your arm feels fresh and your check-in is solid, and a poor fit for the day after a long outing. If you want to see the numbers, the pitching workload calculator shows how an added block changes your ratio, and our guide to workload and arm health explains the research behind building capacity. Pain is a stop sign, not a cue to adjust the grip: stop throwing and see a qualified clinician.

Frequently asked questions

Pitch grips in Pitch AI

Learn the sinker with video, then test it with data

Pitch AI includes a pitch grip video library you can filter by pitch type, handedness, arm slot, role, and pronator or supinator bias, plus pitch design recommendations that suggest a grip starting point, release cues, and short test blocks, and can use ball-flight data you import from TrackMan or Rapsodo. New-pitch work sits inside your throwing program and workload tracking, so a grip experiment never happens off the books.

Sources and further reading

• Baseball Savant (MLB Statcast), Pitch Movement Leaderboard, 2026 regular season, right-handed pitchers
• Driveline Baseball, An Introduction to Seam-Shifted Wakes and their Effect on Sinkers, 2020
• Smith B.L., Seam-Shifted Wake Timeline Part 3, BaseballAero (Utah State University), 2023
• Langin C., Ultimate Guide to Baseball Pitch Grips, Driveline Baseball, 2022
• Premier Pitching Performance, The Science of the 2-Seam Fastball Grip
• Sawchik T., Pitchers are going low, and for good reason, but it's not for everyone, Driveline Baseball, 2026
• Sawchik T., How many fastballs should a pitcher have on the menu?, Driveline Baseball, 2025

Related reading

• Pitch grips: a pitcher's guide to every major pitchEvery grip and movement profile in one place.
• How to throw a four-seam fastballThe riding fastball the sinker is often paired with.
• Why adding another fastball shape can unlock an arsenalWhen a sinker earns a spot next to your four-seamer.
• How to throw a sliderA glove-side breaking ball that plays off a sinker.