mlb glossary // linehype

start_here

elo & the model.

These are the numbers behind the model — our own ratings and how we compare them to the betting market.

ELO
power rating

A single number for how good a team is right now, borrowed from chess (where it ranks players). Every team starts at 1500 — exactly average. Win and your number climbs; lose and it drops. Crucially, beating a great team moves it more than beating a bad one, so the rating quietly accounts for who you've played. Above 1500 = better than average. The gap between two teams' Elo is all you need to estimate who'd win.

1500 = average · 1550+ = strong contender · 1450 = rebuilding
Win Prob
win probability

Our model's estimate of a team's chance to win a specific game — calculated from the Elo gap between the two teams, plus a bump for playing at home.
Implied %
market implied probability

The win chance baked into a betting line. A team at −150 is "implied" to win about 60% of the time. It's the market's opinion, translated into a percentage so we can compare it to ours.

−150 ≈ 60% · −110 ≈ 52% · +130 ≈ 43%
De-vig
removing the house cut

Betting lines include the house's built-in profit margin (the "vig"), which makes both sides add up to more than 100%. We strip it out so the market number is a fair, honest probability — apples to apples with our model.
Edge
model vs. market gap

The difference between our model's win probability and the market's. A big edge means the math and the money disagree — the game worth a second look. It's not a betting tip; it's where two smart estimates part ways.

we flag any gap of 5 percentage points or more

at_the_plate

hitting.

AVG
batting average

How often a batter gets a hit (hits ÷ at-bats). The oldest, simplest hitting stat — but it ignores walks and treats a single like a home run.
.250 average · .300 excellent · .200 is "the Mendoza line"
OBP
on-base percentage

How often a batter reaches base at all — hits, walks, and hit-by-pitches. Better than average because a walk keeps the line moving just like a hit. The first number a smart fan looks at.
.320 average · .370 great · .400+ elite
SLG
slugging percentage

Measures power. Total bases ÷ at-bats, so a home run counts four times a single. High slugging = a hitter who does damage, not just pokes singles.
.400 average · .500 great · .550+ elite
OPS
on-base plus slugging

OBP + SLG in one number — getting on base AND hitting for power. The quickest "is this hitter good?" check there is.
.750 average · .900 great · 1.000 MVP-level
wOBA
weighted on-base average

OPS's smarter cousin. Like on-base percentage, but it weights each way of reaching base by how much it actually helps score runs (a double is worth more than a walk). The stat-head's go-to overall hitting number.
.320 average · .370 great · .400+ elite
BABIP
batting avg. on balls in play

How often balls hit into the field fall for hits. Useful as a luck detector: a number far above normal often means a hitter's been lucky (due for a cooldown), far below means unlucky (due to bounce back).
~.300 is normal for almost everyone

on_the_mound

pitching.

ERA
earned run average

The runs a pitcher allows per nine innings (a full game's worth). The classic pitcher report card — lower is better.
4.00 average · under 3.00 excellent · over 5.00 rough
WHIP
walks + hits per inning

Baserunners allowed per inning. Measures how often a pitcher lets people on, regardless of whether they score. Lower means more traffic-free innings.
1.30 average · 1.10 great · under 1.00 elite
FIP
fielding independent pitching

An ERA-style number built only from what a pitcher controls — strikeouts, walks, and home runs — ignoring his defense and plain luck. Often predicts next year's ERA better than this year's ERA does.
read it on the same scale as ERA
K% / BB%
strikeout & walk rate

The share of batters a pitcher strikes out (good) or walks (bad). Cleaner than the old "per nine innings" versions because it isn't skewed by how long he pitches.
K% 23% average, 30%+ elite · BB% 8% average, under 6% great

the_tracking_era

statcast.

These are the broadcast buzzwords — measured by stadium cameras that track every pitch and batted ball. They describe how something happened, not just the result.

Velo
velocity (pitch speed)

How fast a pitch travels, in miles per hour. The number you hear on every fastball.
avg fastball ~94 mph · 100+ is top-tier heat
Spin Rate
revolutions per minute

How fast the ball spins out of a pitcher's hand. More spin means more movement — a fastball that seems to "rise," or a curveball that breaks harder. It's why two 95-mph fastballs can behave completely differently.
~2,300 rpm average on a fastball
Exit Velo
exit velocity

How hard the ball comes off the bat, in mph. The single best measure of how well a ball was struck.
95+ mph counts as "hard-hit" · 110+ is scorched
Launch Angle
vertical angle off the bat

The up-or-down angle a ball leaves the bat. Too low is a grounder, too high is a pop-up; in between is where line drives and home runs live.
~10°–30° is the damage sweet spot
Barrel%
barrel rate

The share of batted balls hit at the ideal combo of exit velocity and launch angle — "barrels" are the contact most likely to become extra-base hits. More barrels, more damage.
a higher % means consistently elite contact
xwOBA
expected weighted on-base avg

What a hitter's wOBA should be based purely on how hard and at what angle he hits the ball — stripping out luck and great defense. If a hitter's xwOBA is way above his actual wOBA, he's been robbed and good numbers are coming.
compare to wOBA: big gap = luck (good or bad)

the_one_number

war.

WAR
wins above replacement

The most ambitious stat in sports: one number trying to capture a player's total value — hitting, fielding, baserunning, pitching — versus a freely-available "replacement" player (think a quad-A call-up). It answers "how many extra wins did this player give his team?"

2 = solid starter · 5+ = All-Star · 8+ = MVP season
note
why our WAR may differ

WAR isn't one official number — it's computed by outside services (FanGraphs and Baseball-Reference) using their own formulas, so the two versions can disagree by a win or so. When we cite WAR we'll always say whose version it is. Everything else on this page, we compute ourselves from public data — see the methodology.