Data Sources

Attribution

Underlying play-by-play and seasonal stats are sourced from the MLB Stats API. Advanced metrics (xwOBA, exit velocity, barrel %, hard-hit %, etc.) are independently calculated from those raw events by HarryKnowsBall.

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Methodology

Advanced metrics

Statcast-style metrics are derived from MLB Stats API play-by-play events:

• Exit velocity — average launch speed across batted balls with tracked launch data.
• Hard-hit % — share of tracked batted balls with exit velocity ≥ 95 mph.
• Sweet-spot % — share of tracked batted balls with launch angle between 8° and 32°.
• Barrel % — share of tracked batted balls meeting MLB’s barrel definition: exit velocity ≥ 98 mph with a launch-angle window that widens as exit velocity climbs.
• xwOBA — built from a grid of historical outcomes binned by exit velocity and launch angle. Each batted ball is scored against that grid and combined with walks and HBP using level-specific wOBA weights derived from each level’s own run expectancy. The same grid is also expressed as xBA, xSLG, and xERA on the appropriate scales.
• FIP — fielding-independent pitching, derived from a pitcher’s strikeouts, walks, HBP, and home runs. The FIP constant is computed from each level’s own run environment, so a pitcher’s FIP value is anchored to the ERA scale of the level they pitched at.

Cohort percentiles

Players are ranked against same-level and same-league cohorts each season. When a player falls below the qualified sample size for a given metric’s cohort, the percentile is still shown but the bar is rendered with a hatched fill to flag lower confidence in that individual ranking.

Data freshness

Stats refresh nightly during the regular season. Outside the regular season, the pipeline pauses until the next season opens.

Coverage & limitations

Seasons 2015–present are loaded for MLB and the affiliated minor leagues. A few notes on what’s available where:

• Launch-based metrics (exit velocity, hard-hit %, sweet-spot %, barrel %, xwOBA) depend on ball-tracking data and are populated at MLB and AAA only. Lower levels show traditional stats only.
• xwOBA is published for MLB 2020 and later and AAA 2023 and later. Earlier seasons had incomplete launch tracking that would understate the metric, so it is intentionally withheld for those years.
• Per-tracked averages such as exit velocity use only batted balls with recorded launch data. Public sources that impute the untracked remainder may differ slightly as a result.
• Launch metrics are not park-adjusted. Raw exit velocity and barrel rates reflect the ballpark mix each player actually faced.
• Tracking technology has evolved across our coverage window. Pre-2017 pitch velocities in particular are unadjusted and run a touch lower than sources that adjust toward release, so cross-era comparisons should be made with that in mind.

HarryKnowsBall is an independent project and is not affiliated with, endorsed by, or sponsored by Major League Baseball or any MLB team. MLB team names and logos are trademarks of their respective owners.