Definition
The rate at which the batter gets a hit when he puts the ball in play. The calculation for BABIP is (H-HR)/(AB-K-HR+SF). League average is typically .300. A batter with a BABIP of greater than .300 is typically thought of as lucky (though batters with above average speed often have BABIPs greater than .300). A batter with a BABIP lower than .300 is often thought of as unlucky though batters with below average speed often have BABIPs lower than .300. As a rule batters have much greater variance in BABIP than pitchers.

Why does this stat matter for fantasy?
Unlike pitchers, there's no "normal" baseline for BABIP with hitters, as this can fluctuate greatly. A higher BABIP tends to mean the hitter produces a lot of line drives and a high exit velocity, which is a good thing for fantasy value.

Definition
Percentage of fair balls hit in the air, excluding line drives (pop-ups, fly balls).

Why does this stat matter for fantasy?
A batter with a higher fly ball percentage will provide more extra base opportunities, more power, and more RBI.

Definition
Number of fair balls hit in the air, excluding line drives (pop-ups, fly balls).

Why does this stat matter for fantasy?
On average, fly ball hits result in extra bases more often than ground balls.

Definition
Percentage of fair balls hit on the ground.

Why does this stat matter for fantasy?
A high GB% leads to a higher BABIP but lower slugging%.

Definition
Ratio of ground balls to fly balls.

Why does this stat matter for fantasy?
Batters with an extreme grounder ratio have limited homer upside.

Definition
The number of home runs hit by a batter per fly ball.

Why does this stat matter for fantasy?
Batters with a higher home run to fly ball ratio tend to hit more home runs, especially if they also have a high fly ball:ground ball ratio.

Definition
Isolated Power (ISO) measures the power of a batter. The calculation is ISO=SLG% - AVG. Result displays the number of extra bases a player averages per at bat. An ISO of. 200 or higher indicates a hitter with very good power. An ISO of ~.140 will be roughly the league average.

Why does this stat matter for fantasy?
If you are looking for a stat that helps you identify power hitters, ISO is a great stat to use. However, it takes about a full season of data (500-600 ABs) to achieve statistical significance foir ISO. A rookie flashing a high ISO early in the season may not be as likely to maintain his level as player with multiple seasons with high ISO.

Definition
Number of pitches thrown to batter per plate appearance.

Why does this stat matter for fantasy?
Pitches per plate appearance is a measure of a batter's patience and can serve as a leading indicator for higher on-base-percentage.

Definition
Number of runs a batter has generated for his team. This stat measures a player's offensive contribution in total runs. It does so by adding the number of times a batter gets on base to his number of extra base hits and dividing this number by his number of opportunities.

Why does this stat matter for fantasy?
A batter with more runs created is most often a valuable fantasy contributing in a number of categories.

Definition
The percentage of successful stolen bases against attempts.

Why does this stat matter for fantasy?
A player with a low stolen-base percentage may be inclined -- or asked by his team -- to attempt fewer steals, thus hurting his fantasy value. Conversely, a player with a high stolen-base percentage -- provided he is active on the bases -- will likely have more latitude to steal in the future.

Definition
The number of times a batter has struck out looking.

Why does this stat matter for fantasy?
Players with a higher number of strikouts looking may be having issues identifying the strike zone and thus are at risk for producing a lower batting average.

Definition
Number of times a player has been on base.

Why does this stat matter for fantasy?
The more often a batter reaches base, the greater the chance they will score runs. Not recording outs also helps BA.

Definition
Batting WAR (bWAR) measures a player's value as a hitter only by how many more wins he is worth than a replacement-level player at his same position.

Why does this stat matter for fantasy?
bWAR is quick way to view the best hitters in the game. It does not account for base running, so players with the highest bWAR are not always the highest ranked players in fantasy baseball.

Definition
Baserunning Wins Against replacement measures the value of a player's base-stealing performance and their base-running in non-stolen base situations by home many more wins he is worth than a replacement-level player at his same position.

Why does this stat matter for fantasy?
BrWAR is a quick way to identify the best players on the basepaths. Players with a high brWAR are potential sources of runs and stolen bases.

Definition
A stat designed to measure a player's overall offensive contributions per plate appearance based on linear weights.

Why does this stat matter for fantasy?
Typically the biggest fantasy stars grade very well in this category.

Definition
Weighted Runs Above Average measures how many runs a player contributes, compared with an average player. A player with a 0 wRAA would be considered average and a player with greater than 0 wRAA would be considered above average.

Why does this stat matter for fantasy?
In calculating a player's Wins Above Replacement (WAR), which factors a player's offensive and defensive value, wRAA is used to represent the player's offensive contributions.

Definition
The batting average of all opposing batters.

Why does this stat matter for fantasy?
Facing weaker competition increases the chances of success in ERA, WHIP and recording wins and strikeouts.

Definition
The rate at which opposing batters get a hit when they put the ball in play. Calculation is (H-HR)/(AB-K-HR+SF). League average is typically .300. Pitchers with BABIPs above .300 are often considered unlucky, where those below .300 are often considered unlucky.

Why does this stat matter for fantasy?
Pitchers tend to vary less than hitters with regard to BABIP. Fantasy players should expect pitchers with BABIPs above or below .300 to regress to the mean over the course of the season. It makes sense to target pitchers with a BABIP above .300 as they have been unlucky.

Definition
ERA- is a park-adjusted and league-normalized Earned Run Average, where 100 is the league (NL or AL) average. Therefore, a pitcher with a 95 ERA- has a park-adjusted ERA 5 percentage points better than their league’s ERA.

Why does this stat matter for fantasy?
ERA- provides a good overview of a pitcher's value. However, because the data is normalized against the league and adjust for the pitchers home park, a pitchers value may stray from their actual fantasy value.

Definition
Number of fly balls hit in play allowed.

Why does this stat matter for fantasy?
Extreme fly ball pitchers tend to have lower WHIPs but higher ERAs.

Definition
Percentage of fly balls allowed

Why does this stat matter for fantasy?
A pitcher with a high FB rate is more likely to be homer prone.

Definition
Fielding independent pitching (FIP) counts only the events over which a pitcher has the most control: strikeouts, unintentional walks, hit-by-pitches and home runs. It excludes balls hit into the field of play. FIP is expressed numerically the same as ERA.

Why does this stat matter for fantasy?
FIP is a great stat for evaluating pitchers for fantasy baseball to see if they are due for a correction. A pitcher with a low FIP but a high ERA has most likely been unlucky and should be targeted.

Definition
Number of ground balls hit in play allowed.

Why does this stat matter for fantasy?
Ground ball pitchers tend to allow fewer fly balls and therefore fewer home runs and hits that lead to earned runs.

Definition
Percentage of ground balls allowed

Why does this stat matter for fantasy?
The higher a pitcher's GB rate, the fewer home runs they will allow.

Definition
Ratio of ground balls allowed to fly balls.

Why does this stat matter for fantasy?
A high ratio here can lead to a higher BABIP but typically lower ERAs.

Definition
Home-run-per-fly-ball (HR/FB) rate is the rate at which home runs are hit against a pitcher for every fly ball he allows.

Why does this stat matter for fantasy?
A hitter with high home run/fly ball is a good target when looking for home runs. To find players with strong home run tendencies, look for hitters who have both a high fly ball rate and a high HR/FB rate.

Definition
Number of runners inherited (For relief pitchers only).

Why does this stat matter for fantasy?
Preferably the closer enters the game with no runners on base.

Definition
Percentage of inherited runners who scored (For relief pitchers only).

Why does this stat matter for fantasy?
Relief pitchers with a high percentage of inherited runners who scored are not going to help you win your league. These pitchers may not have a high ERA (inherited runners are scored against the pitcher they relieved) but their inability to prevent runs in a high-leverage situation makes them a risky own, especially if they happen to be closers.

Definition
The on base percentage of all opposing batters.

Why does this stat matter for fantasy?
Pitchers with high opponent on-base percentage will have higher WHIPs and are likely to have higher ERAs as well.

Definition
Number of pitches thrown per inning.

Why does this stat matter for fantasy?
The fewer pitches thrown per inning, the more efficient a pitcher is. The more efficient a pitcher is, the deeper they can go in games, giving them a better chance at a win.

Definition
Number of pitches thrown per start.

Why does this stat matter for fantasy?
If a pitcher throws an excessive amount of pitches consistently, their chance of injury increases.

Definition
The slugging percentage of all opposing batters.

Why does this stat matter for fantasy?
Pitchers with high opponent slugging percentage are more victimized by extra base hits and thus are more likely to struggle with ERA.

Definition
Number of inherited runners left stranded (For relief pitchers only).

Why does this stat matter for fantasy?
Relief pitchers with a high strand rates help the departing starters' ERA. A high strand rate also indicates closer potential for set-up men asit demonstrates the ability to succeed in high-stress situations.

Definition
WAR measures a player's value across all aspects of their game (pitching and defense) by how many more wins he is worth than a replacement-level player at his same position.

Why does this stat matter for fantasy?
By itself WAR is more valuable for non-fantasy purposes than for fantasy players. Players with high WAR tend to be more highly ranked in fantasy but because fielding is not used in most leagues, it is less useful than other advanced stats.