Two-Seam Fastball / Sinker
Also known as: two-seamer, sinker, 2-seam
The two-seam fastball is gripped along two seams and typically moves arm-side and downward, inducing ground balls rather than strikeouts.
Gripping along the narrow seams reduces backspin and allows topspin-influenced movement. The result is a pitch that typically runs 1–4 mph slower than the pitcher's four-seamer and breaks toward the throwing arm side while sinking. Ground-ball pitchers prize the sinker because weak contact down in the zone produces easy outs. The movement profile varies significantly by arm slot — higher arm angles produce more horizontal run; lower slots produce more sink.
Example
He lived on his two-seamer, inducing ground balls at a 58% rate by working the bottom of the zone against right-handed hitters.
Why it matters
Distinguishing your two-seamer from your four-seamer in analysis is critical — SwingVantage can flag if your release point is collapsing and blending what should be two distinct pitches.
Related terms
- Four-Seam FastballThe four-seam fastball is the most common pitch in baseball — gripped across all four seams — and is typically the hardest, straightest pitch a pitcher throws.
- Arm AngleArm angle is the vertical orientation of the throwing arm at release — from over-the-top through three-quarter, sidearm, to submarine — and it shapes both the pitch plane and movement profile.
- Horizontal BreakHorizontal break is the lateral movement a pitch generates from spin, measured in inches to the arm side (positive) or glove side (negative).
- Induced Vertical Break (IVB)Induced vertical break is the vertical movement a pitch achieves purely from spin, measured against a hypothetical spinless ball — isolating the Magnus effect from gravity.
- Seam-Shifted Wake (SSW)Seam-Shifted Wake is an aerodynamic effect where an off-center seam orientation disrupts airflow asymmetrically, producing movement that cannot be predicted from spin rate or axis alone.
Related guides & benchmarks
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