Statistics Explained

If you’re unfamiliar with any of the statistics or terms used in our articles, click the link for each term and read the nuts and bolts explanation:

Offensive Statistics:

-wOBA: Weighted on Base Average is a measure of offensive value. It assigns a numerical coefficient to each way of reaching base, then divides by plate appearances. As the linked article says, “not all hits are created equal”, which batting average (and on-base percentage) assumes.
-wRC+: Weighted Runs Created+ is an index that measures a player’s ability to create runs in comparison to the rest of the league. A wRC+ of 100 is perfectly average.
-BABIP: Batting average on Balls in Play is effectively batting average for at bats excluding home runs and strikeouts. It can show how lucky or unlucky a hitter has been depending on batted ball types (line drive%, ground ball%, etc.)
-wRAA: Weighted Runs Above Average is an index that measures the amount of runs a player contributes to the team greater than the average player, with 0 being average. It is calculated using the player’s wOBA and league average wOBA. Generally, 10 wRAA=1 team win.
-UBR: Ultimate Base Running takes into account base running events such as taking the extra base, getting thrown out attempting to take the extra base, not advancing the extra base, tagging up, etc. in order to place a run value on a player’s base running ability.
Pitching Statistics:
-FIP: Fielding Independent Pitching, as the name says, shows how well someone pitched excluding all fielding. It only includes home runs, walks, hit by pitches, and strikeouts. The stat’s goal is to measure what a pitcher’s ERA should have been over a given period, basically putting all pitchers on a level playing field.
-xFIP: Calculated the same way as FIP, except that it replaces the home run total with a league average home run allowed rate times a pitcher’s fly ball rate. This attempts to put pitchers on a more equal playing field and show their true ability.
-SIERA: Another ERA predictor, but a bit more complicated than FIP and xFIP. Unlike the other two above, SIERA includes balls in the field of play, and is adjusted for ballpark and environments.
-PITCHf/x: A system that has been installed in every major league ballpark that tracks pitch velocity, trajectory, movement, location, and ball/strike call accuracy.
Defensive Statistics:
-UZR: Attempts to quantify a player’s defensive skill in terms of runs saved. It takes into consideration things like range, errors, and arm strength in a complex calculation that cannot be explained briefly. It is important to note that it is best to take this stat in 3 year samples to get a good idea of a player’s defensive ability.


-WAR: An all-encompassing statistic that measures a player’s value in terms of wins above a replacement level player. Simply put, a replacement level player is a player that can be easily found in the minor leagues or added to a roster at no marginal cost. A WAR of 0 is considered to be replacement level. For hitters, WAR takes into account wRAA (which uses wOBA in itself), UZR, and UBR. For pitchers, WAR sources primarily from FIP.

-Projection Systems: There are numerous systems such as ZiPS that try to estimate a player’s future performance based on age, past statistics, home ballpark, and many other variables. ZiPS in particular uses three to four years of data, aging trends for similar players, BABIP, and defense independent pitching.

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