MLB Stats Glossary
MLB (aka Major League Baseball) player props glossary: Complete guide to baseball betting stats and abbreviations. Learn batting fundamentals like AVG, OBP, SLG, and advanced Statcast metrics including wOBA, Barrel%, and Exit Velo. Master baseball prop betting terminology on PropsMadness.
General
Def vs
Defensive Rank vs Position
A ranking that measures how well an opposing team defends against a specific position. A lower rank means the defense allows fewer fantasy points to that position.
Note: Rankings and coloring is done in the context of the competition (Playoffs: worst team = 12th, Regular season: worst team = 30th)
Allowed
Allowed
The volume of stats an opponent allows to a specific position compared to other teams. A lower rank means the defense is tougher — they allow fewer stats to that position.
H2H
Head to Head
A direct competition between two teams
CL
Closing Line
The final odds or point spread set by a sportsbook just before a game begins. It reflects the most up-to-date market information and is commonly used as a benchmark for evaluating bet value.
B2B
Back to Back
Scenario where a team plays games on two consecutive calendar days, such as Friday and Saturday
PA
Plate Appearances
Every trip to the plate — hits, walks, HBP, sacrifices, strikeouts all count. Unlike AB, PA never excludes non-hit outcomes. Higher PA volume in a lineup spot = more opportunities to accumulate hits, walks, and other prop-relevant outcomes per game.
AB
At-Bats
Official plate appearances excluding walks, HBP, sacrifices, and catcher's interference. The denominator for batting average. A batter who walks frequently has fewer AB than PA — important context when a hits prop line is set relative to expected at-bat count.
LHB
Left-Handed Batter
Batter who hits from the left side. Generally posts better numbers against right-handed pitchers due to platoon advantages — ball breaks toward the hitter rather than away. When evaluating hits or on-base props, check whether the opposing starter is RHP or LHP.
RHB
Right-Handed Batter
Batter who hits from the right side — the most common handedness in MLB. Tends to perform better against left-handed pitchers. Platoon splits matter when setting lines for individual game props; verify the opposing pitcher's handedness before committing.
LHP
Left-Handed Pitcher
Pitcher who throws from the left side. Typically gives left-handed batters more trouble with breaking balls that move away, while right-handed batters may hold a platoon advantage. Key matchup context for strikeout and hits-allowed prop markets.
RHP
Right-Handed Pitcher
The most common pitcher type in MLB. RHP generally match up more favorably against left-handed batters due to arm angle and breaking ball direction. Critical context for individual batter prop lines — always check RHP vs. LHB/RHB platoon splits.
Batting
AVG
Batting Average
Hits divided by at-bats, the classic hitting metric. Ignores walks and extra-base power, so it can mislead on total offensive value. A direct reference for hits market props.
H
Hits
Any fair ball that allows the batter to reach base without a fielding error or fielder's choice. The foundation of hits prop markets — 1+ hits, 2+ hits, etc. Volume driven by contact rate, batting average, and plate appearances in the lineup spot.
HR
Home Runs
The highest-value hit, worth 4 bases. Heavily influenced by launch angle, exit velocity, ballpark dimensions, and pitcher fly-ball rate (HR/FB%). One of the highest-variance single-game prop markets.
TB
Total Bases
Sum of bases earned on hits: single=1, double=2, triple=3, HR=4. The foundation of total bases prop markets — one of the most popular MLB prop types. Power hitters in favorable park matchups project for higher TB floors and ceilings.
XBH
Extra Base Hits
Doubles, triples, and home runs combined — any hit worth more than one base. Indicates a batter's power output beyond singles. Correlated with exit velocity, ISO, and fly ball tendency against specific pitcher types. Relevant for anytime extra-base-hit props.
OBP
On-Base Percentage
How often a batter reaches base per plate appearance, including walks and HBP that batting average misses. Relevant for hits + walks combined prop markets.Formula: (H + BB + HBP) ÷ (AB + BB + HBP + SF)
SLG
Slugging Percentage
Total bases divided by at-bats, weighting extra-base hits more heavily than singles. Useful for evaluating power hitters in total bases and home run markets.Formula: (1B + 2×2B + 3×3B + 4×HR) ÷ AB
ISO
Isolated Power
SLG minus AVG — measures raw extra-base power with singles stripped out. High ISO batters generate more total bases per hit regardless of contact frequency. Strong predictor for total bases and HR props, especially in hitter-friendly parks.
BB
Walks
Base on balls awarded when a batter takes four pitches outside the zone. Contributes to OBP without registering a hit. Batters with high walk rates reach base more often even when not hitting — relevant for multi-stat props combining hits and walks, or on-base streak markets.
K
Strikeouts
Out recorded when a batter accumulates three strikes. High strikeout rates reduce hits volume and productive plate appearances. Key inverse signal for hits props — compare batter K% against pitcher SwStr% to estimate contact likelihood before setting a line.
SF
Sacrifice Fly
Fly ball out that scores a runner from third base. Counts as a plate appearance but not an at-bat, so it inflates OBP slightly without counting as a hit. Rarely a standalone prop market but affects RBI totals and the PA-to-AB ratio in derived metrics.
SH
Sacrifice Hits
A bunt that advances a baserunner at the cost of an out. Not counted as an at-bat, so it doesn't hurt batting average. Primarily a situational small-sample play with minimal direct prop market impact, but it shifts the PA-to-AB ratio used in some derived stats.
HBP
Hit By Pitch
Awarded when a pitched ball strikes the batter. Counts as reaching base and is included in OBP, but not a hit. Batters who crowd the plate accumulate higher HBP rates, marginally boosting on-base props and OBP-weighted markets like hits+walks combinations.
Advanced Batting
wOBA
Weighted On-Base Average
Assigns a run-expectancy weight to each offensive outcome — walk, single, double, triple, home run. The most predictive single-number offensive efficiency metric in baseball.Formula: (0.69×BB + 0.72×HBP + 0.89×1B + 1.27×2B + 1.62×3B + 2.10×HR) ÷ PA (weights vary by season)
xwOBA
Expected Weighted On-Base Average
wOBA recalculated from exit velocity and launch angle rather than actual results. When xwOBA exceeds actual wOBA, the batter is likely underperforming their contact quality and is a regression candidate — a strong value signal for hits and total bases props.
xBA
Expected Batting Average
Batting average predicted purely from exit velocity and launch angle, ignoring defensive positioning. When xBA significantly exceeds AVG, the batter is likely running into bad luck — regression toward xBA suggests improved hits production ahead.
BABIP
Batting Average on Balls in Play
AVG on all balls put in play excluding HR and strikeouts. League average is around .300. Extreme deviations — high or low — tend to regress. Batters running well below their career BABIP are often underperforming their underlying contact quality, making hits props potentially underpriced.
HH%
Hard Hit Percentage
Share of batted balls with exit velocity at or above 95 mph. High HH% batters make consistently solid contact, sustaining higher xBA and xwOBA over time. A reliable quality-of-contact screen when evaluating hits and total bases prop floors.
B%
Barrel Percentage
Percentage of batted balls combining exit velocity ≥98 mph with launch angle in the 26–30° optimal range. The strongest exit-velocity predictor of home runs and extra-base hits. High barrel rate signals elevated expected total bases and home run prop value.
Plate Discipline
Chase%
Chase Rate
Percentage of pitches outside the strike zone that the batter swings at. High chase rates indicate poor plate discipline and elevated strikeout risk. Key multiplier for pitchers with sharp breaking balls — opposing batters with high Chase% inflate strikeout prop upside considerably.
Zone%
Zone Rate
Percentage of pitches a pitcher throws inside the strike zone. High Zone% pitchers attack the plate more, reducing walk risk but allowing more contact. Relevant context for evaluating over/under strikeout props — pitchers who live in the zone rely on weak contact, not pure whiff rate.
SwStr%
Swinging Strike Percentage
Share of all pitches — balls and strikes alike — that produce swings and misses. The most reliable single pitch-level predictor of strikeout rate. Pitchers with elite SwStr% (above 12%) carry strong strikeout prop floors regardless of zone rate or sequencing.
CSW%
Called Plus Swinging Strike Percentage
Combined rate of called strikes and swinging strikes per pitch — broader than SwStr% alone. Captures both whiff ability and pitch tunneling that freezes hitters. Strong CSW% predicts sustained strikeout volume and is a reliable signal for K-total pitcher props.
F-Strike%
First Pitch Strike Percentage
Rate at which a pitcher throws a first-pitch strike. Pitchers who start ahead in the count more often face fewer deep counts, lower walk risk, and better strikeout setup opportunities. Correlated with lower BB totals and stronger overall K efficiency for strikeout props.
Batted Ball
LD%
Line Drive Percentage
Share of batted balls classified as line drives. Line drives produce the highest BABIP of any batted ball type. Pitchers who allow high LD% face more contact-based hits and tend to post elevated opponent BABIP — a signal that ERA may be understating true risk on hits-allowed props.
GB%
Ground Ball Percentage
Share of batted balls hit on the ground. Ground ball pitchers suppress HR but allow more singles — useful for evaluating run-total props. For batters, high GB% limits total bases and HR upside, which matters when projecting total bases prop ceilings.
FB%
Fly Ball Percentage
Percentage of batted balls that are fly balls. High FB% batters create more HR and total bases opportunities but also more outs in non-HR scenarios. Especially relevant in hitter-friendly parks where fly balls convert to extra bases at higher rates.
FB
Fly Balls
Total count of fly ball batted ball events in a sample. Used alongside HR/FB% to model home run probability — a batter generating many fly balls with a high HR/FB% is a strong HR prop candidate regardless of recent results.
Pull%
Pull Percentage
Share of batted balls hit to the pull side of the field. High Pull% is correlated with elevated HR/FB% because pulled fly balls have the shortest distance to most outfield walls. Key factor when projecting home run prop value for both left- and right-handed hitters.
Pull FB%
Pull Fly Ball Percentage
Percentage of fly balls specifically hit to the pull side. The most direct predictor of home run rate among all batted ball splits — pulled fly balls convert to HR at a significantly higher rate than center-field or opposite-field flies. Highest-signal metric for single-game HR props.
Pitching
ERA
Earned Run Average
Earned runs allowed per nine innings, excluding runs scored due to fielding errors. Lower is better. Affected by park factors, defense quality, and bullpen handoffs.Formula: (ER ÷ IP) × 9
xERA
Expected Earned Run Average
ERA estimate derived from contact quality metrics — exit velocity and launch angle — rather than actual runs allowed. When xERA is lower than ERA, the pitcher may have been unlucky or poorly supported by defense and is a regression candidate for strikeout and hits-allowed props.
FIP
Fielding Independent Pitching
ERA estimator using only outcomes the pitcher fully controls: strikeouts, walks, HBP, and home runs. Removes defensive influence entirely. When FIP is significantly lower than ERA, the pitcher's underlying skills likely exceed their results — a strong predictor of future strikeout prop performance.
SIERA
Skill-Interactive ERA
Advanced ERA estimator that adds batted ball rates to FIP components. Accounts for the fact that ground ball pitchers suppress HR even at similar K and BB rates. More complete than FIP alone for projecting ERA regression and strikeout prop floors across a longer stretch of starts.
WHIP
Walks Plus Hits per Inning Pitched
Baserunners allowed per inning. Strongly correlated with strikeout and walk prop markets for pitchers. Lower is better.Formula: (BB + H) ÷ IP
K/9
Strikeouts per Nine Innings
Rate of strikeouts per nine innings pitched — the standard measure of a pitcher's strikeout ability. High K/9 pitchers carry stronger floors for single-game strikeout total props. Cross-reference with SwStr% and CSW% to confirm the rate reflects true skill rather than sequencing luck.
H/9
Hits per Nine Innings
Hits allowed per nine innings. Heavily influenced by BABIP and team defense — less stable than K/9 or BB/9. Low H/9 is partly luck-driven; pair with xBA and BABIP to determine whether a pitcher's hit suppression is skill-based or defense-aided before projecting hits-allowed props.
HR/9
Home Runs per Nine Innings
Home runs allowed per nine innings. More stable than H/9 as an ERA risk indicator. High HR/9 pitchers are more exposed in HR props for opposing batters. Always park-adjust — a pitcher's HR/9 at Coors Field is not comparable to the same rate at Petco Park.
K-BB%
Strikeout Minus Walk Rate
Strikeout percentage minus walk percentage — the single best combined measure of a pitcher's stuff and command. Elite K-BB% (above 15%) indicates a pitcher who both misses bats and throws strikes. Strong predictor for strikeout prop floors and an inverse signal for walk prop ceilings.
LOB%
Left On Base Percentage
Percentage of baserunners a pitcher strands without allowing to score. League average is around 72%. Extreme LOB% over short samples strongly regresses toward the mean — pitchers with unsustainably high LOB% are ERA regression candidates, more relevant for live betting and inning markets than pre-game props.
HR/FB%
Home Run per Fly Ball Percentage
Rate at which fly balls allowed convert into home runs. League average is roughly 10–11%. Pitchers with elevated HR/FB% are more exposed in hitter-friendly parks. Pair with opposing batters' Pull FB% to identify high-probability HR prop matchups.
Fielding
DRS
Defensive Runs Saved
Fielding metric estimating how many runs a defender saves versus an average player at the same position — positive means above average, negative means below. Impacts BABIP against pitchers: pitchers backed by high-DRS defenders can sustain lower BABIP and hits-allowed rates than their raw contact metrics suggest.
DER
Defensive Efficiency Ratio
Proportion of balls in play converted into outs by the entire defense. Higher is better. A high-DER team suppresses hits per PA for opposing batters, lowering their effective batting average on contact. Relevant for team-level hits markets and for evaluating pitchers who depend heavily on defense to generate weak-contact outs.
