Baseball, more than any other major professional sport, is defined by numbers. Many of the sport’s most hallowed records are immortalized by numbers. 61. 755. .367. 4256. Even casual fans of baseball are familiar with statistics like RBI, batting average, and ERA.
But in the last few decades, statisticians have developed increasingly refined and increasingly complex ways to measure batting, pitching, running, defense, and just about anything else you could think of. More than a few fans have become lost in a sea of acronyms. Is a WHIP of 1.5036 good or bad? If a player has an RISP batting average of .279, should I move him to the middle of the order or trade him? And what is “slugging,” anyway?
Let’s take a crack at breaking down some of these statistics—at least the newer ones.
BA – Batting average: the old standby. A player’s total hits are divided into his total at-bats and expressed as a three-point decimal figure (ex., .223). This statistic is the traditional way to evaluate a player’s offensive ability; if his BA is high, he’s good, and if it’s low, he’s not. A BA of .300 or higher is fairly impressive, while a BA under .200 is generally low enough to get you sent back to the minor leagues. No one has hit over .400 since 1941.
BABIP – Batting average on balls in play: essentially, how often a player reaches base when a ball is hit into play. This discounts home runs and strikeouts, so it’s a measure of how effectively a player can reach base when he hits the ball (or is walked or hit by a pitch). A typical BABIP stays close to .290. It can also be used as a pitching statistic, but we’ll cover that in the pitching section.
OBP – On-base percentage: measures how often a player reaches base. This includes both hits and walks. Traditionally this was ignored in favor of BA, but over the last decade or so, managers have placed an emphasis on players skilled in drawing walks, as a walk gets a man on base as effectively as a hit does. OBP is nearly always higher than BA, simply because walks are included. (A high number of sacrifice flies, coupled with a low number of plate appearances, would result in a lower OBP than BA.) An average OBP today hovers around .340.
A practical application of OBP comes into play when the bases are loaded. It’s not the batting average of the next batter up that matters, it’s his OBP, since getting on base by any method will bring in a run.
RISP – Runners in scoring position: a measure of a player’s BA with runners in scoring position (i.e., on second or third base). Naturally, you’d want a player’s RISP to be high, or else you’ll be leaving runners stranded on the bases. This can also be used as a tool to measure “clutch,” although statisticians disagree on the existence of “clutch”.
SLG – Slugging percentage: a measurement of how many bases a player earns on average per hit. To calculate it, simply divide a player’s total bases (one for singles, two for doubles, etc.) by his total plate appearances. A talented player will have a slugging percentage over .500, though technically, the highest SLG one could achieve is 4.000, if they were to hit only home runs. Seattle pitcher Felix Hernandez hit a grand slam in his only at-bat of the 2008 season, giving him a slugging percentage of 4.000 for the year.
OPS – On-base plus slugging average: simply enough, combining OBP and SLG to create a more complete measurement of a player’s offensive contributions. An OPS of .7000 is deemed average; an OPS of .9000 or higher is likely to lead the league in any given season.
K/9 – Strikeouts per nine innings: a measurement of how many strikeouts a pitcher is likely to record in a game. It tends to be a more reliable measure of a pitcher’s ability to strike out a hitter than raw strikeout totals, since pitchers tire over the course of a game.
K/BB – Strikeout-to-walk ratio: a statistic that measures a pitcher’s control over the ball. A pitcher with a high degree of control over his pitches will record many more strikeouts than walks, resulting in a high K/BB, and vice versa. A strong pitcher will have a K/BB over 5.
BABIP – Batting average on balls in play: as mentioned above, this measures how many balls hit into play end up as hits. This tends to be outside of the pitcher’s control, so an abnormally low BABIP is a sign of a fluky performance. BABIP tends to normalize around .290; pitchers seeing a BABIP higher or lower than .290 can expect to see it regress toward the mean over time.
WHIP – Walks and hits per inning pitched: essentially, the number of runners a pitcher permits to reach base in an inning. This includes, obviously, walks and hits, but also errors, in contrast to ERA. A strong pitcher will have a WHIP near 1.0, meaning they only allow, on average, one baserunner per inning.