Reference
Metric Library
50 terms used on the site, grouped by topic. Definitions are generated from the same constants the model runs on, so the numbers here match the numbers in the projections. Any column header with a dotted underline links here.
Hitting
| wOBA | Weighted On-Base Average. Each way of reaching base is weighted by its run value: uBB 0.690, HBP 0.727, 1B 0.895, 2B 1.270, 3B 1.597, HR 2.058 (2024 league constants), divided by AB + uBB + HBP + SF. Best single-number summary of offense. League average is about 0.316. |
| wRC+ | Weighted Runs Created Plus: ((wOBA − 0.316) ÷ 1.242 + 0.119) ÷ 0.119 × 100. 100 is league average; 150 is 50% better. Computed on park-neutral wOBA on the boards, so it measures talent rather than park. Offense on an easy-to-read scale. |
| AVG | Batting average: hits ÷ at-bats. Ignores walks and extra-base power. |
| OBP | On-base percentage: (H + BB + HBP) ÷ (AB + BB + HBP + SF). Getting on base is the first job of an offense. |
| SLG | Slugging percentage: total bases ÷ at-bats. Rewards extra-base hits. |
| OPS | OBP + SLG. Quick summary; wOBA weights events more accurately. |
| ISO | Isolated power: SLG − AVG. Extra-base hit rate with singles removed. |
| BABIP | Batting average on balls in play: (H − HR) ÷ (AB − K − HR + SF). MLB mean used by the model: 0.291. Heavily luck-influenced for hitters, so projections regress it directly. |
| K% | Strikeouts ÷ plate appearances (batters faced for pitchers). Stabilizes fast, so it is regressed least. |
| BB% | Walks ÷ plate appearances. Projections use unintentional walks. Hitter discipline / pitcher command. |
| uBB | Unintentional walks: BB − IBB. Intentional walks are a managerial choice, not skill. |
| PA | Plate appearances. |
| BF | Batters faced; the pitcher counterpart of PA. |
| HR | Home runs. On MLE tables, home-run factors are per ball in play (see MLE). The most park-sensitive count. |
| SB | Stolen bases, projected from speed, attempt rate and success rate. Minor-league SB/CS are scaled down by level before projecting (AAA ×0.85 down to Rookie ×0.45). |
| UBR | Ultimate base running: non-steal baserunning value. Part of the RUN bucket in WAR. |
| Fld | Fielding runs above average at the player's position (FLD in the WAR breakdown). Blends regressed UZR/DRS/OAA and scouting grades; thin MLB samples lean on scouting. |
| CFraming | Catcher framing runs: strikes added or lost versus a league-average framer. |
Pitching
| FIP | Fielding Independent Pitching: (13×HR + 3×BB − 2×K) ÷ IP + a constant (3.10 in projections). Strips out defense and sequencing luck. A better predictor of future ERA than ERA is. Lower is better. |
| FIP+ | League ERA ÷ player FIP × 100. Above 100 is better than average. Pitching counterpart of wRC+. |
| ERA | Earned run average: earned runs × 9 ÷ IP. Projected ERA blends FIP, SIERA and prior ERA. |
| ERA+ | League ERA ÷ player ERA × 100, park-adjusted. |
| HR/BF | Home runs per batter faced. Pitchers' home-run rate is regressed hardest of the three outcomes. |
| TBF/G | Batters faced per game: about 26-29 for starters, far fewer for relievers. Role signature used in comp matching. |
| SP/RP | Role classification: SP when the recency-weighted starts share is at least 50%. |
Value and WAR
| WAR | Wins Above Replacement. Hitters: BAT (wOBA-derived runs) + RUN (SB/CS + UBR) + FLD + POS (positional adjustment) + REP (replacement credit), converted at 9.8 runs per win. Pitchers: FIP-based runs prevented versus a replacement pitcher (replacement FIP 5.40 SP / 4.55 RP), at 9.5 runs per win (display tables use a pitcher-specific runs-per-win). One number for total value. Shown park-adjusted by default; boards offer a park-neutral view. |
| RPW | Runs per win: 9.8 for hitters and 9.5 for pitchers, calibrated to the recent run environment. |
| Replacement Level | What a freely available call-up produces. Pitchers: FIP 5.40 (SP) and 4.55 (RP), blended between 60 and 100 projected IP when the role is unknown. |
| Park-neutral | A stat or projection with the park (and, for minor leaguers, the league level) stripped out. Boards that say MLE or neutral use this frame. |
Translation (MLE)
| MLE | Minor League Equivalency. Each component rate (BB, HBP, K per PA; 1B, 2B, 3B, HR per ball in play) is park-neutralized, multiplied by a league or level factor, adjusted for batted-ball mix and age versus the level, and rebuilt into wOBA/ISO/BABIP. Example hitter factors, Triple-A: K ×1.20, BB ×0.69, HR ×0.70. Pitchers (level-wide): Triple-A K ×0.88, BB ×1.05, HR ×1.10. Puts every league on one scale. Worked example and every factor: MLE Factors page. |
| Level factor | The multiplier for a stat at a league or level. Above 1.00 means the stat rises against MLB pitching (hitter strikeouts); below 1.00 means it falls. |
| Reliability | How much a plate appearance at a level counts as MLB-quality evidence when seasons are blended: hitters MLB 1.00, AAA 0.75, AA 0.50, A+ 0.35, A 0.25, Rookie 0.12. |
| Age vs level | Player's age minus the level's average age. Younger hitters get a small boost in translation (+1.5% per year, capped at +5%); older hitters a small discount (−1.0% per year, capped at −6%). Shown on the MLE boards. |
| Basis chips | RAW = as recorded; CTX = projection in park/league context; A+C = actual so far plus context projection; MLE = level/park-neutral translation. Shown on player-page rows. |
| MLB% | Share of a player's projected playing time expected at the MLB level (call-up and optioning odds). Projected WAR on the boards is before this discount; headline values multiply by it. |
| ETA | OGILVIE's projected MLB arrival year: the first year MLB% passes 40%. Not a scouting ETA. |
Projection method
| Marcel | Forecasting method that weights the prior three seasons and regresses toward the league mean. Weights (most recent first): hitters 6/4/2, pitchers 6/3/1. Each season's PA or BF is first discounted by level reliability. |
| Regression | Pulling a rate toward the league mean in proportion to how little evidence there is: blended = (evidence × rate + prior strength × mean) ÷ (evidence + prior strength). Prior strength by stat is on the Methodology page. |
| Aging Curve | Per-stat year-over-year change derived from historical paired seasons, corrected for survivorship (players who dropped out are imputed as replacement-level seasons). |
| Statcast | MLB's tracking data (exit velocity, launch angle, sprint speed, velocity). Used for percentile bars and some scouting-grade inputs. |
| ROS | Rest of season: the projection for what remains of the current season. Actual-so-far plus ROS = full-season estimate. |
| ROS_FRAC | Fraction of the season remaining at build time (1 − days elapsed ÷ season days, season window late March to late September). Read as 1.0 in the offseason (current setting 1.00). |
Prospects
| OFP | Overall Future Potential: 20-80 scouting grade of a prospect's ceiling. 50 = MLB regular, 60 = above-average starter, 70 = All-Star. |
| FV | Future Value: same scale as OFP. |
Contracts and trade value
| Conf% | Confidence applied in Trade Value: rises with MLB experience from 0.55 (no MLB PA; 0.50 under age 22) through 0.78 at 500 PA to 1.00 at 3,000+ PA (innings converted at 4.5 PA each), with a floor set by prospect grade (0.45 unranked to about 0.80 for a top-10 prospect). Reflects bust risk for unproven players. |
| NPV | Net present value: future dollars discounted 10% per year, applied to both projected value and owed salary. |
| $/WAR | Market price of a win: $8.0M in 2027, growing 3% per year; relievers priced at a discount. |
| Arb-1/2/3 | Arbitration years 1-3. Projected salary is a share of the free-agent value of the player's WAR: 25% / 42% / 62%, with caps of $12M / $22M / $32M. |
| Super-2 | Players with 2.123 to under 3.000 years of service get an extra (fourth) arbitration year; modeled at 18% of free-agent value. |
| CBT | Competitive Balance Tax. The model assumes a $238M threshold in 2027, growing 4% per year, as the budget cap in Free Agent Room calculations. |