MLB Betting Definitions

The batting average on all batted balls that actually land in the field of play (excluding home runs). League average is around .300. A very high BABIP (.360+) often indicates luck that will regress; a very low one (.230-) suggests unlucky results that should improve. We use BABIP deviation vs. xwOBA to identify regression candidates in trend analysis.

SharpSignal's composite environmental score that combines density altitude, wind direction, and wind speed into a single 0–150 number. 100 = neutral sea-level conditions, calm wind. Above 110 = elevated carry (favors overs, HR props). Below 90 = suppressed carry (favors unders, pitchers). Displayed as a color-coded gauge in the Park & Weather tool.

The percentage of batted balls hit in the 'barrel' zone — exit velocity above 98 mph at a launch angle between 26° and 30°, a range that historically produces a .500+ batting average and 1.500+ slugging percentage. A barrel rate above 12% is elite; below 4% is well below average. Barrel rate is the strongest predictor of home run probability and is the primary ranking signal in the HR Hitter Finder.

A measure of recent workload for a team's relief corps — typically tracked as total pitches thrown in the last 3 days. High bullpen stress means available relievers are fatigued, which increases the odds of the starter going deep or of a tired bullpen yielding late runs. The Game Script tool shows 3-day pitch count stress alongside 7-day WHIP and K/9 for each team's bullpen.

Career head-to-head history between a specific batter and pitcher. We show career plate appearances, hits, home runs, batting average, and xwOBA in the Hit Script. Minimum 5 PA for the stat to be shown — below that, the sample is too small to be meaningful. BvP is a secondary signal, not a primary one, but significant career history (20+ PA) at extreme values is worth noting.

A 0–100% number representing how strongly our model believes in its prediction, independent of odds. A high confidence (75%+) means the model's features are strongly aligned. Confidence does not equal edge — a high-confidence pick at bad odds can still have no betting value. Both confidence and edge are shown together so you can evaluate each pick on both dimensions.

The percentage of all pitches that result in either a called strike or a swinging strike. CSW captures both command (getting borderline pitches called) and stuff (generating swings-and-misses). A CSW above 30% on any pitch is elite. It's a more complete measure of pitch dominance than whiff rate alone.

A physics calculation combining actual altitude, temperature, and humidity to determine effective air density. Less dense air (high altitude, hot, dry) causes baseballs to carry further — increasing home runs and scoring. The formula used by our models: Density Altitude = Altitude_ft + 118.8 × (Temp_F − 59) + 1.2 × (100 − Humidity%) × 100. Coors Field at altitude is the extreme case, but a hot August day at Globe Life Field can rival it temporarily.

The difference between our model's probability estimate and the market's implied probability (derived from consensus odds). Edge Score = Model Probability − Market Implied Probability. A positive edge means our model sees a better chance than the market is pricing. An edge of 5% or more on a market with reasonable odds is considered a significant signal. Zero or negative edge picks are still shown as informational signals but are not flagged as strong value.

The speed of the ball off the bat measured in mph via Statcast radar. Higher exit velocity means harder contact. Average exit velocity above 91 mph is considered above average for a full season. We track season average EV, max EV (hardest single ball), and L5 average EV (last 5 games) to identify players coming on or falling off in power output.

A betting market on the combined run total through the end of the third inning. The F3 model isolates starter quality — since relievers rarely appear before the 4th — and heavily weights TTO1 performance, umpire K-bias, and the top of each team's batting order vs. the opposing starter's platoon splits. Bullpen stress is deliberately excluded from the F3 model since it's almost always irrelevant.

The percentage of games in which a team scores at least one run in the first inning. A team with a 45% F1% scores in the first inning almost half the time — relevant for NRFI (No Run First Inning) bets. Shown in the Team Splits page alongside home/road and day/night records.

The percentage of batted balls hit at 95 mph or harder. A simpler cousin of barrel rate — it captures all hard contact regardless of launch angle. Hard hit rate above 40% is above average. It's a good indicator of raw contact quality even for line-drive hitters who don't elevate much.

ISO = Slugging Percentage minus Batting Average. It measures raw extra-base power by stripping out singles. An ISO above .200 is considered plus power; below .100 is contact-only. We use it to assess how much a lineup or individual batter punishes mistake pitches.

A mathematical formula for optimal bet sizing: Kelly% = Edge / (Decimal Odds − 1). SharpSignal uses fractional Kelly (25% of full Kelly) by default, which reduces variance while capturing most of the long-run growth. Kelly units are shown on picks with positive edge and available odds. A full Kelly stake on every pick is too aggressive for real-money bettors — the fractional approach is the standard for professional bankroll management.

No Run First Inning / Yes Run First Inning. A binary market on whether either team scores in the top or bottom of the first inning. NRFI bets win if both half-innings are scoreless. Our NRFI model uses pitcher TTO1 K rates (first time through the order), umpire K-bias, park run factor, and team F1 scoring tendencies derived from thousands of historical first innings.

A multiplier that adjusts for how a specific ballpark affects run scoring, home runs, or strikeouts relative to a neutral environment (100 = neutral). A HR park factor of 115 means 15% more home runs are hit at that venue than average — favoring overs and HR props. A run park factor of 88 suppresses scoring. Park factors account for dimensions, altitude, air density, and prevailing wind patterns over multiple seasons.

The historical percentage of games at a specific ballpark where the total runs scored exceeded the posted over/under line. A park with a 58% over rate is structurally favorable for overs regardless of the individual matchup — dimensions, altitude, prevailing wind, and foul territory all contribute. SharpSignal's Park O/U History page shows over rate, under rate, average posted line, average actual total scored, and O/U margin (actual minus line) for every MLB venue. Pushes are excluded from rate calculations.

SharpSignal's composite matchup number: the difference between a batter's xwOBA vs. the actual pitcher hand today vs. their overall season xwOBA. A positive platoon score means the batter has a structural advantage in today's handedness matchup; negative means a structural disadvantage.

The performance difference a batter shows depending on whether the pitcher throws left-handed or right-handed. Most hitters hit better against same-side pitchers (LHB vs. LHP, RHB vs. RHP is an exception — opposite-hand matchups are usually advantageous). A strong platoon split means the handedness matchup matters a lot for that batter today. The Hit Script calculates each batter's xwOBA vs. the opposing pitcher's hand.

A start in which the pitcher goes at least 6 innings and allows 3 or fewer runs (not necessarily earned). Quality start rate over the last 5 starts (L5 QS%) is shown on the Starting Pitchers page as a measure of recent durability and effectiveness. A QS rate above 60% in the L5 window indicates a starter who is deep and reliable right now; 0% means the pitcher has been pulled early or gotten hit in recent outings.

The average run differential per game when a specific umpire is behind the plate vs. the league average. Positive RPG bias = more runs scored on average under this umpire. Negative = fewer runs. This is a secondary signal used alongside K-bias when evaluating total markets.

MLB's version of the point spread. The standard run line is -1.5 for the favorite (they must win by 2 or more runs) and +1.5 for the underdog (they cover even with a 1-run loss). Unlike football, the run line changes the odds dramatically — a -200 moneyline team might be -110 on the run line because 1-run games are common in baseball. Our run line model is calibrated specifically for margin-of-victory prediction, not just win probability.

An advanced ERA estimator that predicts what a pitcher's ERA should be based on his true skill profile — strikeout rate, walk rate, and ground ball/fly ball/popup mix. Unlike ERA (affected by sequencing and defense) or even FIP (which ignores batted ball type), SIERA accounts for the non-linear interaction between strikeouts and ground balls: a high-K pitcher who also generates ground balls is harder to score on than his individual rates suggest. Lower SIERA = better pitcher. League average is around 4.10. SharpSignal shows SIERA on the Starting Pitchers page and uses it as a feature in game total and run line models.

The percentage of batted balls hit between 8° and 32° launch angle — the range that produces hits at the highest rate. Sweet spot contact is less selective than barrel rate and captures high-quality line drives and low fly balls that don't meet the strict barrel exit velocity threshold.

Each time a starting pitcher faces the opposing batting lineup from top to bottom is one 'time through the order.' Pitchers are measurably less effective the third time through (TTO3) as hitters pick up spin and sequencing patterns. Our TTO splits show K rate by TTO1/TTO2/TTO3, identifying which pitchers fall apart in the 5th–6th inning vs. which ones maintain stuff deep into games.

The drop in pitcher effectiveness from TTO1 to TTO3. A pitcher with a large decay (e.g., K rate drops from 28% to 16% by the third pass) is a strong Under candidate in innings 5–7 and signals that the bullpen will be needed early. The Game Script tool shows each starter's TTO3 K rate as a proxy for late-game danger.

A z-score measuring how many more (or fewer) strikeouts an umpire generates per game compared to the league average, based on their full historical record. A z-score of +1.5 means the umpire calls strikes at a rate 1.5 standard deviations above average — a significant pitcher advantage that inflates K totals and suppresses run scoring. We weight this into pitcher K milestone probabilities and game total projections.

The percentage of individual pitches that produce a swing-and-miss. Higher whiff rates mean more strikeouts and harder-to-barrel pitches. A whiff rate above 30% on a specific pitch type (e.g., a slider) makes that pitch nearly unhittable. We show per-pitch-type whiff rates in the Hit Script to identify which pitch a batter is most vulnerable to.

A comprehensive offensive metric that weights each offensive outcome (single, double, triple, HR, walk, HBP) by its actual run value. More accurate than OBP or SLG alone because it accounts for the real scoring impact of each event. League average is approximately .320. We use team wOBA to measure lineup strength in the Game Script tool.

A version of FIP that replaces a pitcher's actual home run total with the expected number of home runs based on his fly ball rate (since HR/FB rate regresses to league average over time). xFIP isolates the pitcher's skill by removing defense, sequencing, and home run luck. A lower xFIP means the pitcher is expected to give up fewer runs going forward. League average is typically around 4.00–4.20. SharpSignal shows xFIP alongside SIERA on the Starting Pitchers page — together they give a fuller picture of a pitcher's true quality than ERA alone.

A Statcast metric that measures a hitter's (or pitcher's) expected offensive value based purely on contact quality — exit velocity and launch angle — rather than actual outcomes. A ball hit at 105 mph at 28° is credited the same whether it's caught by a leaping outfielder or lands for a double. xwOBA removes luck from batting average and is the best single-number predictor of future offensive performance. League average is approximately .315. We use it as the primary contact quality signal in the Hit Script and Exit Velocity tools.