Glossary
Pitching
Stuff+: Pitch quality graded only on physical traits (velocity, movement, spin, release point, extension, arm angle, and gaps from the pitcher’s primary fastball). 100 is an average qualified MLB pitcher; 10 points is one standard deviation. Pitch-level grades are scaled within fastballs, breaking balls, and offspeed pitches. How it’s built.
RV+: Actual run value per 100 pitches, on the same scale as Stuff+.
IVB (induced vertical break): How far a pitch finishes above or below where a spinless pitch would, in inches. High-IVB fastballs “ride”; curveballs have negative IVB.
HB (horizontal break): Sideways movement in inches, positive toward the pitcher’s arm side for both righties and lefties, so shapes compare directly.
CSW rate: Called strikes plus whiffs, divided by pitches.
Chase induced: Share of pitches outside the zone that the hitter swung at.
Hitting
Chase rate: Swings at pitches outside the strike zone ÷ pitches outside the zone. Bunt attempts are excluded.
Zone swing / zone contact: Swing rate on pitches in the zone, and contact rate on those swings.
Whiff rate: Swinging strikes ÷ swings. Foul tips count as whiffs, matching Baseball Savant.
Hard-hit rate: Share of balls in play hit 95+ mph.
EV90: The 90th-percentile exit velocity on balls in play. A steadier read on raw power than average or max exit velocity.
xwOBA: Expected weighted on-base average. Uses the expected value of each ball in play from exit velocity and launch angle, plus actual strikeouts, walks, and hit-by-pitches.
Conventions
Percentiles rank a player against the qualified league pool (150+ PA or batters faced) and are oriented so higher is always better, so a low chase rate or a low walk rate allowed shows as a high percentile. Unqualified players are placed against the same qualified pool.
Δ14 compares the final (or most recent) 14 days with the season to date. Rates are in percentage points. Why two weeks is enough for some numbers and not others.
Strike zone means Statcast zones 1–9.