The tunnel

Two pitches, one tunnel.

Deception is shared early flight. From the same arm slot, two pitches look like one out of the hand and only separate once the hitter has committed. Pick any two filed pitches and watch the shape split: which way each pitch wants to finish, and which one sets up the other.

Pitch APitch B

Handedness

Four-seam

rides, stays true

The late split

Same release and tunnel, then each breaks its own way late.

Slider

holds flat, sweeps glove-side

Four-seam specimen →Slider specimen →Why tunneling works →

The endpoints are each pitch's sourced shape direction, taken from the specimen records. Both pitches leave a shared release, run together through the tunnel window, and split late toward those endpoints. How far each path bows on the way, and how late it leaves the shared line, follow the pitch's own spin character (a four-seam holds its line; a slider stays in the tunnel and cuts late and short), but the whole thing is a schematic of the shared-release idea, not a measured trajectory. A hitter's real reaction window depends on the arm, the release, and the pitch sequence. For the full picture of why tunneling works, see Sequencing & Tunneling.

The tracked tunnel data (release points, separation in inches, the record) lives with the record-keepers. Pitch Atlas does not estimate it here: Baseball Savant ↗ and the FanGraphs model primer ↗. How to read them is its own wing: Reading Models.