What is a Sinker? Definition and Examples
A sinker is a fastball variant with arm-side run and downward movement that induces ground balls, thrown 88-96 mph with a spin axis tilted toward the throwing arm.
What is a Sinker?
A sinker is a fastball variant designed to drop and run toward the pitcher's arm side rather than ride straight through the zone like a four-seamer. It surrenders a few ticks of velocity and several inches of induced vertical break in exchange for steep downward movement at the plate, which jams hitters into pounding the ball into the ground. Some pitchers and coaches use "two-seam fastball" interchangeably with sinker; Statcast classifies them as the same pitch type (SI). The sinker is the primary ground-ball weapon in modern pitching arsenals.
How a Sinker Is Thrown and Measured
The sinker grip places the index and middle fingers along the two parallel seams running with the throwing motion. The ball comes out of the hand with reduced backspin and a spin axis tilted toward 1:00-2:00 for a right-handed pitcher (10:00-11:00 for a lefty). That tilted axis converts rotational energy into Magnus force pulling the ball down and arm-side instead of straight up.
Statcast measures three numbers that define a sinker:
- Velocity: 88-96 mph, 1-3 mph slower than the same pitcher's four-seamer
- Induced vertical break (IVB): 2-10 inches, versus 14-20 for a four-seamer
- Horizontal break: 12-20 inches of arm-side run, roughly double a four-seamer
Spin rate runs 1,900-2,300 RPM. Spin efficiency is often above 90%, but the axis is what matters — the angle, not the inefficiency, creates the sink.
A Worked Example: Logan Webb
Logan Webb of the San Francisco Giants is the modern archetype. In 2024 he threw his sinker 47% of the time at 92.7 mph average velocity, with 5.4 inches of induced vertical break and 16.8 inches of arm-side run. That combination produced a 58% ground-ball rate against the pitch — eight points above league average for sinkers and 25 points above the four-seam league rate. Webb's sinker is not a swing-and-miss pitch; it generated a 13% whiff rate on the year. It racks up double-play groundballs and chases weak contact instead.
Compare Framber Valdez, who throws his sinker 94 mph with a similar profile, and Clay Holmes, whose 96-97 mph sinker produced one of the highest ground-ball rates in baseball during his Yankees tenure.
Why the Sinker Matters
Sinker-heavy pitchers thrive when paired with strong infield defense and ground-ball-friendly parks. Front offices specifically pair these arms with rangy middle infielders. Sinker usage league-wide bottomed out around 2020 as the four-seam-up-in-the-zone trend took over, but it has rebounded since 2023 as hitters adapted to elevated heat. The pitch is also a lower-stress alternative to riding a four-seamer at maximum effort, which has implications for Tommy John surgery risk profiles.
For DRS-positive defenses, a sinkerballer can post a FIP 0.30 runs higher than his actual ERA over a full season, because the metric undervalues weak-contact suppression.
Limitations and Misconceptions
A sinker is not a sinker if it doesn't sink. Many pitchers throw what is classified as a two-seamer that produces only 2-3 inches of separation from their four-seam IVB — these "cement-mixers" play like flat fastballs and get hit hard. Statcast's classification is grip-based via spin axis, not movement-based, so a poorly executed two-seamer still appears as SI in the data. Sinkers also underperform against opposite-handed hitters (a righty sinker tails into a lefty's barrel) and against uppercut, low-ball-hunting hitters built to lift sinkers.
Related Terms
- Cutter — the glove-side counterpart to the sinker
- Spin rate — the underlying input to all pitch movement
- Whiff rate — sinkers trade whiffs for grounders
- Stuff+ — quantifies sinker quality versus league
- Hard hit rate — sinkers suppress this on contact
In Legends Deck
Sinker-primary pitcher cards in Legends Deck carry a GROUNDBALL trait that reduces line-drive rates in simulated plate appearances and elevates double-play conversion when runners are on first. Webb-archetype cards trade strikeout output for elite WHIP suppression, making them ideal anchors for defense-heavy rosters built around your top OAA infielders.