Guide · Baseball · Pitching
Pitch tunnels: the geometry of a hitter's mistake.
A major-league hitter has about 175 milliseconds to decide whether to swing. In that window, the pitch is only 30 feet down the plate. If two pitches look identical at 30 feet — and separate after — the hitter is guessing. That corridor is called the tunnel, and the best pitchers build their whole arsenal around it.
The commit point
Pitch to plate is about 60 feet 6 inches. A 95 mph fastball covers that in around 400 ms. Human visual processing and swing initiation take roughly 175 ms. Subtract that from 400 and the hitter's decision has to be made when the ball is still 23–25 feet from home plate — the commit point.
After the commit point, the hitter is a passenger. The pitch does whatever the pitch was going to do.
The tunnel
A pitch tunnel is a narrow imaginary cylinder — roughly the size of a baseball — that a pitch passes through at the commit point. Two pitches tunnel if their positions coincide there, even if their release, movement and final location differ. The hitter sees identical balls at 25 feet. He decides. Then the pitches separate.
A well-tunneled fastball / slider pair might share a corridor 3 inches wide at commit, then separate by 14 inches at the plate. The hitter who guessed fastball swings under a slider. The hitter who guessed slider watches a fastball down the middle.
Why release matters more than movement
Tunneling is not primarily about how much a pitch breaks. It is about how similar two pitches look for the first 35 feet. Release height, release side, extension, arm slot, initial velocity vector — these decide whether two pitches share a tunnel. Movement after commit is the payoff, not the setup.
This is why "release consistency" is the highest praise in pitch design. A change-up thrown from a lower slot than the fastball is not a real change-up. A slider that leaves the hand pointing three feet left of the fastball is a slider the hitter has already identified.
The geometry, roughly
Tunnel score ≈ Δlocation_commit ⁄ Δlocation_plate Δlocation_commit distance between two pitches at ≈25 ft from plate Δlocation_plate distance between the same two pitches at 0 ft Smaller commit gap + larger plate gap = better tunnel. Elite pairs score below ≈0.2.
Movement helps only insofar as it lands after the commit point. Ten inches of break that all happens before 25 feet is ten inches of warning. Ten inches of break that all happens after 25 feet is a swing-and-miss.
What the engine will simulate
The Ball Physics Baseball engine — in build — resolves every pitch deterministically from release vector, spin axis, spin rate, seam orientation and drag. That means you can pair any two pitches and measure their actual tunnel: where they overlap, where they separate, and what the batter's commit point would have looked like from the box.
Baseball is a physical game played on a mental clock. Tunnels are the geometry of that clock.