What is Blocking Runs? Definition, Measurement, and Example

What is Blocking Runs?

Blocking runs is a Statcast metric that quantifies a catcher's ability to keep pitches in front of him. It measures how many runs a catcher saves or costs his team by blocking balls in the dirt — or failing to — compared to a league-average catcher given the same pitches in the same situations. It's the third pillar of modern catcher defense, alongside catcher framing and throwing.

How Blocking Runs is Measured

Statcast assigns every pitch a catcher faces a block probability based on its location, velocity, movement, and pitch type, plus the game situation (runners on base, count). A spiked curveball with a runner on third might have a 60% block probability; a fastball at the letters is near 100%.

For each pitch:

• If the catcher blocks a pitch with a 70% block probability, he earns +0.30 blocks above average (1 − 0.70).
• If he lets it by, he's charged −0.70 (0 − 0.70).

These blocks above average are then converted to runs using the run value of a passed ball or wild pitch in that base-out state — a ball that gets by with a runner on third costs far more than one with the bases empty.

A Real Example

Elite blockers like Austin Hedges and Jonah Heim have posted seasons of +5 to +8 blocking runs, meaning their glovework in the dirt alone saved roughly a win's worth of runs over a year (10 runs ≈ 1 win). The separation comes on the hardest chances: average catchers block roughly 80% of true "tough" pitches in the dirt, while the best blockers get over 90%. Over 6,000+ pitches caught per season, that gap compounds quickly. Poor blockers run the same math in reverse — a −5 blocking runs season is a real, measurable drag on run prevention that never shows up in ERA discussions but absolutely belongs there.

Why Blocking Runs Matters

Blocking was historically invisible — lumped into passed balls, which are scorer-judgment calls and ignore difficulty entirely. Blocking runs finally prices it. Front offices use it in catcher valuations and contract negotiations; pitchers use it when deciding whether they can bury their best swing-and-miss pitch with two strikes. A catcher who can't block effectively takes away a pitcher's splitter and back-foot slider with runners on. For fantasy, blocking skill correlates with playing time for defense-first catchers.

Limitations and Misconceptions

Blocking runs is not the same as passed balls — a catcher can have zero passed balls and still grade poorly because he was rarely tested, or because wild pitches were charged to the pitcher. It also doesn't capture framing or game-calling. And like all catcher metrics, it depends partly on the pitching staff: a staff full of high-spin sweepers generates more difficult blocking chances than a fastball-heavy staff.

In Legends Deck: Catcher blocking grades feed into wild pitch and passed ball frequency in simulation — pair your dirt-heavy pitchers with a high-blocking backstop.

Related: Catcher Framing · Pop Time · Wild Pitch · Passed Ball