Home Topics Terms

OPSOn-base Plus SluggingOn-base percentage plus slugging percentage. One number for how often a hitter gets on base and how many bases his hits are worth.
AVGBatting AverageHits divided by at-bats. Plate appearances that aren't at-bats, like walks, hit-by-pitches and sacrifices, are left out.
ERAEarned Run AverageHow many earned runs a pitcher allows per nine innings. Runs that score because of fielding errors don't count.
K%Strikeout RateThe share of a player's plate appearances ending in a strikeout. Pitchers want it high, hitters want it low.
BABIPBatting Average on Balls In PlayThe rate at which balls hit into fair territory, home runs aside, become hits.
WARWins Above ReplacementAn estimate of how many fewer games a team would have won with a readily available fill-in, a replacement player, in this player's place.
Exit VelocityThe speed of the ball as it comes off the bat. It measures how hard each batted ball was hit.
VelocityPitch VelocityHow fast a pitch is thrown. Statcast measures it at the moment the ball leaves the pitcher's hand.
FPCTFielding PercentageHow often a fielder handles a chance without making an error.
wOBAWeighted On-Base AverageAn on-base average that weights each way of reaching base, from a walk or single up to a home run, by how many runs it's actually worth.
wRC+Weighted Runs Created PlusThe run value a hitter created, adjusted for league and ballpark and scaled so the league average is 100. A 120 means 20% more runs than an average hitter.
FIPFielding Independent PitchingA number built only from outcomes the pitcher decides on his own (home runs, walks, hit batters and strikeouts), put on the same scale as ERA.
xFIPExpected Fielding Independent PitchingFIP with actual home runs swapped for expected ones: fly balls allowed times the league-average rate of home runs per fly ball. It reads on the ERA scale.
BarrelA batted ball whose exit velocity and launch angle land in the combination that almost always goes for extra bases.
HardHit%Hard-Hit RateThe share of a hitter's batted balls that come off the bat at 95 mph or faster.
OAAOuts Above AverageHow many more (or fewer) outs a fielder made than an average fielder would have.
Spin RateHow many times per minute the ball rotates as it leaves the pitcher's hand, measured in rpm.
xwOBAExpected wOBAThe wOBA a batter's contact should have produced on average, judged by exit velocity and launch angle rather than by what actually happened to each ball.
SIERASkill-Interactive Earned Run AverageAn ERA estimate built from strikeouts, walks and the mix of ground balls and fly balls, with the formula also accounting for how those pieces interact. The result is in ERA units.
CSW%Called Strikes + WhiffsThe percentage of all pitches that are either taken for a called strike or swung at and missed.
IVBInduced Vertical BreakThe up-and-down movement a pitch gets from its spin alone, with gravity taken out. Measured in inches.
VAAVertical Approach AngleThe downward angle of a pitch as it reaches home plate. The closer to 0°, the flatter it comes in.
Stuff+Stuff PlusGrades a pitch on its physical traits alone, leaving out where it was thrown. An average pitch scores 100.
Bat SpeedHow quickly the hitter swings, in mph, measured 6 inches in from the end of the barrel.
BlastA swing that is both fast and squared up. Statcast bat tracking keeps a separate count of them as its mark of a good swing.
Attack AngleWhether the bat is traveling up or down, and how steeply, at the instant its sweet spot meets the ball.
Swing TimingA set of metrics that breaks down whether a swing was in sync with the ball, in time and position, when the bat got closest to it.

Based on the 2026 MLB season

SabermetricsHandbook

Basic stats

OPSOn-base Plus Slugging
AVGBatting Average
ERAEarned Run Average
K%Strikeout Rate
BABIPBatting Average on Balls In Play
WARWins Above Replacement
Exit Velocity
VelocityPitch Velocity
FPCTFielding Percentage

Advanced stats

Swing Timing2026
Attack Angle2025
Bat Speed2024
Blast2024
xwOBAExpected wOBA
SIERASkill-Interactive Earned Run Average
CSW%Called Strikes + Whiffs
IVBInduced Vertical Break
VAAVertical Approach Angle
Stuff+Stuff Plus

Topics

Hitting

AVGBatting Average
OPSOn-base Plus Slugging
wOBAWeighted On-Base Average
wRC+Weighted Runs Created Plus

Player Value

wRC+Weighted Runs Created Plus
WARWins Above Replacement

Contact Quality

Exit Velocity
HardHit%Hard-Hit Rate
Barrel
xwOBAExpected wOBA

Luck vs. Skill

BABIPBatting Average on Balls In Play
xwOBAExpected wOBA

Pitching

ERAEarned Run Average
FIPFielding Independent Pitching
xFIPExpected Fielding Independent Pitching
SIERASkill-Interactive Earned Run Average

Strikeouts and Whiffs

K%Strikeout Rate
CSW%Called Strikes + Whiffs

Pitch Quality

VelocityPitch Velocity
Spin Rate
IVBInduced Vertical Break
VAAVertical Approach Angle
Stuff+Stuff Plus

The Swing

Bat Speed
Blast
Attack Angle
Swing Timing

Fielding

FPCTFielding Percentage
OAAOuts Above Average

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