A quick-reference glossary of the metrics used across the EdgeRanked AI MLB tools. Definitions are written for everyday baseball fans — no math degree required.
How to use this glossary
Modern baseball analysis leans on a handful of recurring ideas: rate stats that are fair to compare across players, expected metrics that separate skill from luck, and park factors that adjust for where a game is played. The definitions below are grouped loosely from the raw building blocks (contact quality, strikeout rates) up to the composite scores that combine them. You don't need to memorize the formulas — just the intuition for what each number is telling you and which direction is 'good.'
Metric definitions
- K% (Strikeout Rate)
- The share of plate appearances (for hitters) or batters faced (for pitchers) that end in a strikeout. Already rate-based, so it's the fairest way to compare strikeout tendencies. Higher is good for pitchers; lower is good for hitters.
- Opponent K%
- The strikeout rate of the lineup a pitcher is facing, ideally split by pitcher handedness. High opponent K% means a more strikeout-friendly matchup.
- SwStr% (Swinging-Strike Rate)
- The percentage of a pitcher's total pitches that hitters swing at and miss. A stable, predictive measure of bat-missing ability that often leads changes in strikeout totals.
- PutAway% (Put-Away Rate)
- With two strikes, how often a pitcher finishes the hitter off with a strikeout. Isolates the ability to close out at-bats rather than just generate early whiffs.
- Arsenal Whiff%
- How often the pitches in a pitcher's repertoire generate swings and misses, rolled up across the arsenal. A relatively matchup-independent read on raw stuff quality.
- Barrel%
- The share of a hitter's batted balls struck with the exit-velocity-and-launch-angle combo that historically yields elite results. The gold-standard indicator of quality power contact.
- Hard-Hit%
- The percentage of batted balls hit at 95 mph or harder. A broad, stable measure of authoritative contact and the raw material of power.
- Exit Velocity
- How fast the ball leaves the bat. Average exit velocity reflects consistency of contact; peak exit velocity reflects raw power ceiling. Stabilizes quickly in small samples.
- xSLG (Expected Slugging)
- An estimate of what a hitter's slugging percentage should be based on contact quality (exit velocity and launch angle) rather than results. The gap vs. actual slugging flags luck in either direction.
- xwOBA (Expected Weighted On-Base Average)
- A single expected-value stat that credits a hitter for the quality of every plate appearance — walks plus expected outcomes on contact — on the wOBA scale where higher is better. A strong all-in-one measure of a hitter's underlying production, and of what a pitcher is allowing.
- Park Factor
- An index (100 = league average) for how much a ballpark boosts or suppresses an outcome. Above 100 helps the outcome; below 100 suppresses it.
- HR Factor (Home Run Factor)
- The park factor specifically for home runs, often split by batter handedness. Driven by dimensions, wall heights, and altitude.
- Power Score / Power Delta
- A composite that summarizes whether a hitter's recent batted-ball quality (barrels, hard-hit rate, exit velocity, xSLG) is trending up or down versus their season baseline.
- Pitcher Matchup Score
- A 0–100 grade of how favorable a starting pitcher's strikeout matchup is, blending K%, opponent K%, recent form, stuff quality, workload, and park/weather. 90+ Elite, 60–69 Neutral, below 60 Weak.
- Pitcher Vulnerability Index
- A 0–100 ranking of how exposed a starting pitcher is to power and hard contact, built from allowed exit velocity, barrel and hard-hit rates, xSLG/xwOBA against, and HR rate, adjusted for park and weather. Higher means more vulnerable.
- wOBA (Weighted On-Base Average)
- A rate stat that weights each offensive outcome by its real run value — a home run counts far more than a walk — to summarize a hitter's total production on a single scale. xwOBA is its contact-quality-based expected version.
- Launch Angle
- The vertical angle at which the ball leaves the bat. Combined with exit velocity, it determines whether hard contact becomes a line drive, a home run, or a harmless fly ball. The 'barrel' zone is a specific launch-angle-and-speed sweet spot.
- Whiff%
- The share of a hitter's (or against a pitch's) swings that miss. Closely related to swinging-strike rate, but measured per swing rather than per pitch — a direct read on swing-and-miss.
- ISO (Isolated Power)
- Slugging percentage minus batting average, isolating extra-base power by stripping out singles. A quick gauge of how much of a hitter's production comes from extra-base hits.
- Run Factor
- The park factor for total run scoring (100 = average). Captures doubles and triples, not just home runs, so a park can be run-friendly without being homer-friendly.
- Rest / Workload
- How much a pitcher is expected to throw and on how many days' rest. More projected innings mean more chances to accumulate strikeouts; short rest or a limited leash caps the ceiling.
Want to see these metrics in action? The MLB Analytics Lab puts them to work across the live tools, and the companion guides go deeper on matchup scores, park factors, strikeout analytics, and power trends.