The Legend

Every number on this site, defined in plain language. The methodology page explains how the signals are built and validated; this page explains what they mean when you meet one.

No baseball jargon left behind

The FVR signals

The numbers we compute ourselves. These are the product.

EV95: A hitter's 95th-percentile exit velocity, in mph — how hard he hits the ball when he really connects. We use the 95th percentile instead of the average because top-of-range contact is the skill and mishits dilute the average. It is the most stable metric in our engine (year-over-year r = 0.88), which means it travels forward in time better than any batting average. In our current MLB sample the lightest regulars sit near 98–100 and the loudest near 112.
Luck gap (park-adjusted): Actual results on contact minus what the launch physics say those batted balls should have produced, adjusted for park. Positive: results running ahead of the contact quality underneath them — fade shape. Negative: contact getting underpaid — breakout shape. The gap is mostly transient. It tends to close, in both directions, which is exactly what makes it a signal.
Overlay score: The composite breakout signal: contact quality and the luck gap combined into one number, scaled so that higher means more breakout-shaped. On our pre-registered out-of-sample holdout, the top quintile of this score outgained the bottom by +1.15 annualized WAR. Important boundary: it ranks who is likely to out-perform their current value — not who is best.
xVal (MLB grid): For AAA hitters: their batted balls graded on the MLB value grid — as if each ball in play had been struck in a big-league park. It projects contact quality across the promotion. Honest boundary: our signals are holdout-validated at the MLB level; the AAA application is the frontier.
Stuff-lite: Our pitch-quality grade, built from physical pitch characteristics and calibrated on MLB pitches. It is stability-validated (year-over-year r = 0.87) but not yet outcome-validated, which is why pitchers are watchlist rows, never calls. And stuff is not command.
Balls in play (BIP): Sample size: how many batted balls a hitter's signals are measured on this season. More is more trustworthy; treat anything under about 100 with caution — we flag the small ones ourselves.
Pitches: Sample size for the stuff grade: how many tracked pitches the grade is computed from.
Last 14 days: The player's line over the trailing two weeks, straight from MLB's public data, refreshed nightly. Absent when a player hasn't appeared in the window.

Context numbers

Numbers we borrow, with the source named.

The Index: Tracked, not flagged. Three wings, all data-defined and refreshed nightly: the top 25 qualified bats by season WAR (MLB's calculation), the top 10 pitchers by the same — tracked ungraded, because our arm signals aren't outcome-validated yet — and the consensus top 25 prospects (FanGraphs Board, snapshotted weekly), each shown next to what our engine grades. Every Index page carries a computed explanation of why no board flagged him. A flag means the engine found a mispricing; the Index means we're watching. The distinction is the product.
The Wire: Short summaries of what X is saying about a player — on the field and on cardboard — over the trailing week. Built by searching X posts date-scoped to that window (summarized by Grok, xAI); when there are fewer than a handful of relevant posts, the track reads quiet rather than inventing a take, and a summary is never allowed to draw on anything older than the window. Every strip carries its as-of date. Tones: ▲ hot, △ warm, ▼ cold, ▬ quiet. It is chatter, not signal — the boards do not read it and it does not move a call.
WAR (season · MLB calc): Wins Above Replacement — a player's total value versus a replacement-level fill-in, denominated in wins. Rough guide: 2 is a solid regular, 4 an All-Star case, 6+ an MVP conversation. Not ours: the season WAR on player pages is MLB's own calculation, pulled from the same public API as everything else and refreshed nightly. When a ledger call cites WAR it uses FanGraphs' version and says so — the flavors differ by a few tenths, which is why we always name the source.

Ledger terms

The vocabulary of being on the record.

Call: A falsifiable prediction: filed with a metric, a threshold, a window, and a timestamp. Nothing about a call is edited after filing.
Metric: The quantity a call is judged on. Currently three kinds: results on contact vs baseline (park-adjusted value on contact, measured against where it stood at filing), WAR added from filing (FanGraphs WAR accumulated after the filing timestamp), and MLB debut by window end.
Threshold: The number the metric must clear for the call to be a HIT.
Baseline: Where the metric stood at the moment of filing — the starting line the threshold is measured from.
Window: The date the call resolves. No extensions, no exceptions.
Resolves by computation: When the window closes, the engine computes the metric and stamps HIT or MISS. Nobody argues, and nobody grades their own homework.
HIT · MISS · OPEN: Resolved in our favor; resolved against us; window still open. The record on every page counts all three, because a hit rate with the misses removed is marketing, not measurement.
Correction: If we discover an error mid-window, the correction is appended in public and noted on the call. The original filing stays as filed.

The card terms

The hobby’s vocabulary, for readers three months into collecting. No card jargon left behind either.

Raw: An ungraded card, straight out of the pack or the binder — no professional grade, no protective slab. Raw prices run well under graded prices for the same card because the buyer is taking the condition risk themselves.
PSA / BGS: The two big professional grading companies. You mail them a card; they inspect the corners, edges, surface, and centering, score it 1–10, and seal it in a labeled plastic slab. A graded card trades on the label, which is why the same card can be worth a few dollars raw and a hundred slabbed.
PSA 10 / BGS 10: The top of the scale — PSA calls a 10 Gem Mint; a BGS 10 (Pristine) is rarer still because Beckett grades four subcategories and all of them have to hit. That scarcity is why a BGS 10 usually prices above a PSA 10 of the same card, and why the jump from a 9 to a 10 is the steepest step in the hobby.
Flagship (as we use it): The single card of a player we price nightly — chosen as the most liquid card of his we can verify, so the trend line tracks one real market instead of an average of thin ones. It is not necessarily his most valuable card; a Bowman 1st autograph will usually out-price it. It is the card whose price actually moves with news.
The rookie slot (as we use it): The second card in a player's rack: the highest-volume card from his earliest card year — for modern players that lands on the hobby's benchmark (a first Bowman or rookie-year Chrome). When a prospect's only real card is both his flagship and his rookie, the rack collapses to one and says so.
Parallel / numbered: The same card printed in scarcer variants — different colors, foils, or refractors, often serial-numbered (a card marked /99 has ninety-nine copies). Scarcer parallel, higher price, thinner market. Names in brackets in our flagship line — [Black], [Refractor] — are parallels.

Reading a stat line

The standard abbreviations on player pages and boards.

Abbr.	Meaning
G	Games played.
AB	At-bats (walks and sacrifices don't count).
R	Runs scored.
H	Hits.
AVG	Batting average — hits per at-bat.
OPS	On-base plus slugging: the quickest one-number hitter summary. Rough guide: .700 fringe, .800 good, .900 star.
HR	Home runs.
RBI	Runs batted in.
SB	Stolen bases.
BB	Walks (bases on balls).
B/T	Bats / throws (L, R, or S for switch).
IP	Innings pitched — the decimal is thirds of an inning, so 71.2 means 71⅔.
W–L	Wins and losses credited to the pitcher.
SV	Saves — games finished protecting a narrow lead.
ERA	Earned run average — earned runs allowed per nine innings.
SO	Strikeouts.
WHIP	Walks plus hits per inning pitched — baserunners allowed. Under 1.10 is excellent; 1.40+ is trouble.
Lvl	Level: MLB, then the minor-league ladder — AAA, AA, A+ (High-A), A (Single-A).
MLB CAREER	The bold row at the bottom of a player's table: career totals, majors only.
Total	A season split across two teams, combined — shown alongside each stint.

The credibility numbers

The fine print on the homepage cites an RE24 correlation of 0.975 — that is our computed run values checked against FanGraphs’ for 2024 qualified batters — and a pre-registered holdout of 721 batter-seasons, meaning the entire test protocol was frozen before we looked at the data it would be judged on. The full story, including the bug we disclosed and the finding that didn’t flatter us, lives on the methodology page.