Glossary

Percentage of pitches that are strikes (called or swinging).

Percentage of pitches thrown in the strike zone.

Percentage of plate appearances starting with a strike.

Percentage of pitches on the edge of the strike zone. Measures ability to paint corners.

Percentage of pitches in the heart of the strike zone. Lower is better — middle-middle pitches get crushed.

Percentage of pitches thrown well outside the zone (waste pitches). Used for setting up hitters.

Percentage of pitches in the shadow zone (just off the edge). Tests umpire judgment — higher shadow usage often leads to more called strikes.

Grades raw pitch quality using physics — velocity, spin, movement, release point, and tunneling. Isolates what the pitch does independent of location or sequencing. 100 = league average.

Grades pitch command and placement. Measures how well pitches target effective zones, accounting for count, batter tendencies, and the strike zone. 100 = league average.

Combined overall pitch grade blending stuff, location, sequencing, and batter context into a single score. The most comprehensive per-pitch metric. 100 = league average.

How well a pitcher's repertoire works together as a unit. Measures interaction effects between pitch types — velocity gaps, movement diversity, tunneling quality, and arsenal composition. 100 = average, higher = better synergy.

What you bring to the mound — velocity gaps, movement diversity, pitch balance, and raw pitch quality. 100 = average.

How you use what you've got — tunneling, sequencing unpredictability, and speed deception. 100 = average.

Measures how much harder a pitcher is to hit than expected based on raw pitch characteristics. Derived from bat tracking residuals analyzing swing decisions and contact quality. 100 = average, higher = more deceptive. Available 2024+.

Average arm angle at release (degrees). 0 = sidearm, 90 = overhand.

Changeup (CH) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Changeup (CH) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Changeup (CH). How much more or less vertical force the pitch has than expected given the arm slot.

Changeup (CH). How much more or less horizontal force the pitch has than expected given the arm slot.

Changeup (CH). How much more or less the ball rises than expected given the arm slot (inches).

Changeup (CH). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Curveball (CU) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Curveball (CU) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Curveball (CU). How much more or less vertical force the pitch has than expected given the arm slot.

Curveball (CU). How much more or less horizontal force the pitch has than expected given the arm slot.

Curveball (CU). How much more or less the ball rises than expected given the arm slot (inches).

Curveball (CU). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Four-Seam Fastball (FF). How much more or less the ball rises than expected given the arm slot (inches).

Four-Seam Fastball (FF). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Cutter (FC) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Cutter (FC) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Cutter (FC). How much more or less vertical force the pitch has than expected given the arm slot.

Cutter (FC). How much more or less horizontal force the pitch has than expected given the arm slot.

Cutter (FC). How much more or less the ball rises than expected given the arm slot (inches).

Cutter (FC). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Four-Seam Fastball (FF) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Four-Seam Fastball (FF) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Four-Seam Fastball (FF). How much more or less vertical force the pitch has than expected given the arm slot.

Four-Seam Fastball (FF). How much more or less horizontal force the pitch has than expected given the arm slot. Positive = more arm-side run than expected.

Splitter (FS) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Splitter (FS) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Splitter (FS). How much more or less vertical force the pitch has than expected given the arm slot.

Splitter (FS). How much more or less horizontal force the pitch has than expected given the arm slot.

Splitter (FS). How much more or less the ball rises than expected given the arm slot (inches).

Splitter (FS). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Horizontal acceleration (ft/s²). Measures the rate of lateral movement — higher magnitude means sharper break.

Vertical acceleration (ft/s²). Measures spin-induced lift or drop relative to gravity. Higher = more rise, lower = more drop.

Horizontal movement (inches). Arm-side positive for RHP. Measures how much the pitch moves laterally due to spin and seam effects.

Vertical movement / induced vertical break (inches). Positive = rise relative to gravity. Measures how much spin fights gravitational drop.

4-seam fastball induced vertical break (inches).

4-seam fastball induced horizontal break, arm-side normalized (inches).

4-seam fastball combined movement magnitude (inches).

Sinker induced vertical break (inches).

Sinker induced horizontal break, arm-side normalized (inches).

Sinker combined movement magnitude (inches).

Cutter induced vertical break (inches).

Cutter induced horizontal break, arm-side normalized (inches).

Cutter combined movement magnitude (inches).

Slider induced vertical break (inches).

Slider induced horizontal break, arm-side normalized (inches).

Slider combined movement magnitude (inches).

Sweeper induced vertical break (inches).

Sweeper induced horizontal break, arm-side normalized (inches).

Sweeper combined movement magnitude (inches).

Curveball induced vertical break (inches).

Curveball induced horizontal break, arm-side normalized (inches).

Curveball combined movement magnitude (inches).

Changeup induced vertical break (inches).

Changeup induced horizontal break, arm-side normalized (inches).

Changeup combined movement magnitude (inches).

Splitter induced vertical break (inches).

Splitter induced horizontal break, arm-side normalized (inches).

Splitter combined movement magnitude (inches).

Pitch movement in inches.

Induced vertical break (inches). Positive = rise relative to gravity. Measures how much spin fights gravitational drop.

Induced horizontal break (inches). Arm-side positive for RHP. Measures lateral movement due to spin.

Percentage of pitches that are 4-seam fastballs.

Percentage of pitches that are sinkers.

Percentage of pitches that are cutters.

Percentage of pitches that are sliders.

Percentage of pitches that are sweepers.

Percentage of pitches that are curveballs.

Percentage of pitches that are changeups.

Percentage of pitches that are splitters.

Percentage of total pitches for this pitch type.

Average pitch speed (mph) for this pitch type.

4-seam fastball average velocity (mph).

Sinker average velocity (mph).

Cutter average velocity (mph).

Slider average velocity (mph).

Sweeper average velocity (mph).

Curveball average velocity (mph).

Changeup average velocity (mph).

Splitter average velocity (mph).

Fastball minus changeup velocity differential (mph).

Sinker (SI) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Sinker (SI) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Sinker (SI). How much more or less vertical force the pitch has than expected given the arm slot. Positive = more rise than expected.

Sinker (SI). How much more or less horizontal force the pitch has than expected given the arm slot.

Sinker (SI). How much more or less the ball rises than expected given the arm slot (inches).

Sinker (SI). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Slider (SL) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Slider (SL) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Slider (SL). How much more or less vertical force the pitch has than expected given the arm slot.

Slider (SL). How much more or less horizontal force the pitch has than expected given the arm slot.

Slider (SL). How much more or less the ball rises than expected given the arm slot (inches).

Slider (SL). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Average spin rate across all pitches (rpm).

Pitch spin rate in revolutions per minute (rpm).

Sweeper (ST) vertical acceleration from spin (ft/s²). Unlike iVB, not affected by pitch speed so faster pitches aren't penalized.

Sweeper (ST) horizontal acceleration from spin (ft/s²). Unlike iHB, not affected by pitch speed so faster pitches aren't penalized.

Sweeper (ST). How much more or less vertical force the pitch has than expected given the arm slot.

Sweeper (ST). How much more or less horizontal force the pitch has than expected given the arm slot.

Sweeper (ST). How much more or less the ball rises than expected given the arm slot (inches).

Sweeper (ST). How much more or less the ball moves horizontally than expected given the arm slot (inches).

Pitcher's fastest fastball variant (FF, SI, or FC) by avg velocity. Must be 20%+ of fastball usage to qualify.

Maximum pitch velocity recorded (mph).

Average pitch speed across all pitch types (mph).

Average fastball speed (mph). Includes 4-seam, sinker, and cutter.

Maximum pitch speed recorded (mph).

Average pitch velocity in miles per hour (mph).

Ground ball percentage. Percentage of batted balls that are ground balls.

Fly ball percentage. Percentage of batted balls that are fly balls.

Line drive percentage. Percentage of batted balls that are line drives.

Infield fly ball percentage. Percentage of fly balls that are infield flies.

Pull percentage. Percentage of batted balls hit to the pull side.

Center percentage. Percentage of batted balls hit to center field.

Opposite field percentage. Percentage of batted balls hit to the opposite field.

Fly ball pull percentage. Pulled fly balls are the most likely to leave the yard — lower is better for pitchers.

Percentage of batted balls hit to center field.

Hard-hit ball percentage. Batted balls with exit velocity 95+ mph.

Medium contact percentage. Batted balls with moderate exit velocity.

Soft contact percentage. Weakly hit batted balls.

Barrel rate. Batted balls with optimal exit velocity and launch angle combination.

Average exit velocity on batted balls against (mph).

Maximum exit velocity on batted balls against (mph).

Average launch angle on batted balls (degrees).

Percentage of batted balls hit at the ideal launch angle (8-32 degrees). Lower is better for pitchers.

Percentage of batted balls with low exit velocity (under 89 mph). Higher is better for pitchers.

Percentage of batted balls that are topped/rolled over (negative launch angle). Higher is better for pitchers — topped balls are weak grounders.

Percentage of batted balls hit under the ball (very high launch angle, typically pop-ups). Higher is better for pitchers.

Overall expected run value per 100 pitches across all pitch types (xwOBA-based, BABIP-neutral). Negative = runs prevented (good).

Expected Run Value per 100 pitches using xwOBA on batted balls. Negative = runs prevented (good). More stable year-to-year than RV.

4-Seam fastball expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Sinker expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Cutter expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Slider expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Sweeper expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Curveball expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Changeup expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Splitter expected run value per 100 pitches (xwOBA-based, BABIP-neutral).

Swinging strike rate. Percentage of swings that miss the ball.

Chase rate. Percentage of pitches outside the zone that batters swing at.

Swing rate on pitches outside the strike zone.

Swing rate on pitches in the strike zone.

Overall swing rate on all pitches.

Contact rate on swings at pitches outside the zone.

Contact rate on swings at pitches in the zone.

Overall contact rate when swinging.

Swinging strike percentage (swinging strikes / total pitches).

Called strike percentage. Pitches taken for strikes.

Called strikes + whiffs percentage. Combined measure of pitch effectiveness.

First pitch strike percentage. How often the pitcher starts the at-bat with a strike.

Percentage of two-strike pitches that result in a strikeout. Measures finishing ability.

Strikeout rate. Percentage of batters faced who strike out.

Walk rate. Percentage of batters faced who walk.

Strikeout rate minus walk rate. Measures command and strikeout ability.

Home run rate. Percentage of batters faced who hit a home run.

Home runs per fly ball. Percentage of fly balls that become home runs.

Three True Outcomes percentage. Strikeouts + walks + home runs divided by PA.

Batting Average on Balls In Play. Hits on balls in play divided by balls in play.

Left On Base percentage. Percentage of baserunners who don't score. (FanGraphs)

Batting average against. Opponents' batting average.

Weighted On-Base Average against. Comprehensive offensive value allowed. (FanGraphs)

Context-dependent run value from Statcast delta_run_exp. Used in heatmaps. Negative = good for pitcher.

Overall run value per 100 pitches across all pitch types. Runs saved vs average. (FanGraphs)

Fastball run value per 100 pitches. Runs saved vs average fastball. (FanGraphs)

4-seam fastball run value per 100 pitches. Runs saved vs average 4-seamer. (FanGraphs)

Sweeper run value per 100 pitches. Runs saved vs average sweeper. (FanGraphs)

Sinker run value per 100 pitches. Runs saved vs average sinker. (FanGraphs)

Cutter run value per 100 pitches. Runs saved vs average cutter. (FanGraphs)

Slider run value per 100 pitches. Runs saved vs average slider. (FanGraphs)

Curveball run value per 100 pitches. Runs saved vs average curveball. (FanGraphs)

Changeup run value per 100 pitches. Runs saved vs average changeup. (FanGraphs)

Splitter run value per 100 pitches. Runs saved vs average splitter. (FanGraphs)

Win Probability Added. Impact on team's win probability. (FanGraphs)

Run Expectancy based on 24 base-out states. Runs saved vs average. (FanGraphs)

Clutch performance score. Performance in high-leverage situations vs overall. (FanGraphs)

Average leverage index when entering games. Measures situation importance. (FanGraphs)

Average leverage index when the pitcher enters the game. Higher = more high-pressure situations. 1.0 = average leverage.

Whiff rate in high-leverage situations (LI > 1.5). Measures ability to miss bats when it matters most.

Total strikeouts recorded.

Total walks (bases on balls) issued.

Total swinging strikes generated.

Doubles plus triples plus home runs.

Total bases from hits: one for a single, two for a double, three for a triple, and four for a home run.

Pitches thrown per inning pitched. Measures efficiency.

Pitches thrown per plate appearance.

Pitches per inning pitched. Measures efficiency — lower means more economical outings.

Average pitches per start. Measures workload capacity and efficiency.

Percentage of plate appearances starting with a strike. Getting ahead in the count is a strong predictor of success.

Fielding Independent Pitching. Estimates ERA using only strikeouts, walks, and home runs.

Expected FIP. Normalizes home run rate to league average HR/FB ratio.

Skill-Interactive ERA. Advanced metric accounting for batted ball types and sequencing. (FanGraphs)

Expected ERA based on quality of contact allowed. (FanGraphs)

Strikeout/walk ERA estimator. Uses only K% and BB% to estimate ERA — a simple but predictive metric. Lower is better.

ERA minus expected FIP. Positive = underperforming, negative = outperforming xFIP expectations. Larger gaps suggest luck or defense influence.

Combined z-scores across BABIP, LOB%, HR/FB%, and ERA-FIP, weighted by consistency (% of seasons beating league average). Positive = consistently defying luck, negative = luck victim.

Expected HR/FB% computed from Barrel% and fly ball spray direction (pull + oppo). Pitchers whose actual HR/FB% is consistently below this value are suppressing home runs through skill, not luck.

Composite Score is a summary rank built from multiple component signals instead of a single raw stat. On hitter luck pages, it combines the standardized gaps between actual and expected results across the tracked luck indicators so one number can capture who is most outperforming or underperforming contact-quality expectations overall. It is best used as a sorter that points you toward the strongest combined outliers, then followed by the component stats for context.

AVG minus xBA compares a hitter's actual batting average to the expected batting average estimated from contact quality. Positive values mean more hits fell in than the contact model would project, which can reflect good fortune, speed, spray skill, or weak spots in defensive positioning. Negative values mean the hitter turned quality of contact into fewer hits than expected.

SLG minus xSLG compares a hitter's real slugging percentage to the expected slugging percentage implied by contact quality. Positive values mean the hitter converted contact into more total bases than the model expected, while negative values mean the outcomes lagged behind the quality of contact. This is useful for spotting hitters whose extra-base damage has recently run hotter or colder than their underlying batted-ball profile.

wOBA minus xwOBA compares actual overall offensive value to the value expected from strikeouts, walks, and quality of contact. Positive values mean the hitter's recent results have outperformed the expectation model, while negative values mean they have gotten less run value than the model would project. Because wOBA captures more than just hits, this is the broadest of the expected-vs-actual hitter gap stats.

Expected ERA minus expected FIP. Negative values indicate a pitcher is suppressing contact quality beyond what their strikeout/walk profile suggests — a sign of real skill, not luck.

Earned Run Average. Earned runs allowed per 9 innings pitched.

ERA minus FIP. Positive = ERA higher than expected (unlucky or poor defense). Negative = ERA lower than expected (lucky or good defense).

Measures luck and sequencing. Positive values mean ERA is higher than expected (unlucky — results worse than contact quality suggests). Negative values mean ERA is lower than expected (lucky — results better than contact quality suggests). Values near zero indicate results matching expectations.

Walks + Hits per Inning Pitched. Baserunners allowed per inning.

Wins Above Replacement. Total value compared to a replacement-level player. (FanGraphs)

Home runs allowed per 9 innings pitched.

Single-game offensive run value totals the change in run expectancy created by everything a hitter did in that game. Each plate appearance adds or subtracts value based on how much it improved the offense's expected runs in that situation, then those values are summed into one game score. Positive values mean the hitter created more run value than an average offensive game, while negative values mean the hitter's outcomes reduced expected scoring relative to average.

Trend Score is a recent-form indicator, not a season-long talent grade. It blends what the hitter has done lately, how well they have been striking the ball, and whether the sample is large enough to trust. Higher scores point to a hitter whose current rolling window is stronger than the rest of the pool after balancing performance quality with playing-time stability.

Similarity Score measures how closely another hitter season matches the selected hitter's offensive profile across the dimensions used by the model, such as contact quality, plate discipline, production shape, and batted-ball tendencies. It is a relative matching score rather than a universal grade, so the most useful read is comparing candidates within the same similar-hitters list. Higher scores indicate a closer overall match to the reference season.

Player's age during the season.

Number of games started as a pitcher.

Total innings pitched in the season.

Number of games pitched.

Innings Pitched. Total innings pitched.

Total number of pitches thrown.