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Pitch Atlas

Fastball

Alias

Running Fastball

aka moving fastball · two-seamer · sinker

Not really its own pitch. It's just a nickname for a two-seamer or sinker that mostly runs sideways toward the pitcher's arm side instead of dropping. Same grip, different label.

Schematic baseball cover. This pitch has no filed seam geometry yet — the grip and shape below are sourced in words, not measured here.

The grip

Not a separate grip — it is the run-dominant end of the two-seam and sinker family, named for the arm-side horizontal action rather than the sink.

Reputable analysisMLB.com Glossary — Two-Seam Fastball

What it does

Heavy arm-side run with less drop focus; MLB lists 'running fastball' and 'moving fastball' directly among the names a two-seamer goes by.

Reputable analysisMLB.com Glossary — Two-Seam Fastball

What it really is

An alias for the run-heavy two-seam/sinker rather than a distinct pitch — MLB's own glossary files it as a nickname for the two-seam fastball.

Reputable analysisMLB.com Glossary — Two-Seam Fastball

Who throws itUsed colloquially for any pitcher whose two-seamer or sinker is run-dominant.

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.