Breaking ball
Knuckle-Curve (Spike Curve)
A curveball with a firmer grip. You spike one fingertip into a seam for a stronger hold, which often gives a tighter, harder break. Despite the name it has nothing to do with a knuckleball, so most players just call it the spike curve.
The grip
Gripped and thrown like a curveball, but the index finger is spiked — the fingernail or knuckle dug into a seam and raised off the surface — giving a firmer anchor on the ball; the middle finger rests along a seam as usual.
What it does
Functions essentially as a curveball, often with a tighter, harder break than the standard grip. Despite the name it has nothing to do with a knuckleball, which is why players and coaches usually just call it the spike curve.
Who throws itOften called the 'spike curve' by MLB players and coaches
Study this first
Spiking a fingertip into a seam only firms up the hold; the pitch still functions as a curveball. The filed 12-6 Curveball is the break to study underneath the spike grip.
Basic file
This pitch has a sourced one-line grip and movement and an honest explanation, not yet a filed specimen with authored grip geometry and a full craft chapter. A fuller breakdown is coming. Sourced, not corrected.
Others in the breaking ball