Understanding Sabermetric Baseball Statistics

Sabermetrics can give us incredible insight into just how effectively baseball players are performing. But before you can use these numbers to impress your friends, you need to understand them.

Sabermetrics have come into prominence because of the shortcomings of traditional baseball statistics. Some of the numbers that aren't very trustworthy are obvious; most people know that simply relying on wins or saves does not give you a good picture of a pitcher's effectiveness, for instance. Less well known is how misleading statistics like batting average and ERA can be. While these statistics are certainly correlated with a player's value, the relationship is rather crude; it is often the case that a player with a much lower batting average can still be a more effective hitter than his high-average counterpart.

Luckily, we have other stats that paint a better picture of a player's value than the traditional ones we've known since we were children.

The Basics

If there is one non-traditional statistic every fan should know, it's On-Base Percentage (OBP). This number tells us what percentage of the time a player reaches base, and is calculated in a manner similar to batting average. Simply divide the number of times a player reaches base safely (without recording any outs) by the number of plate appearances by the batter. This simple stat has recently come into wide usage, and for good reason - it is one of the best indicators of a hitter's value, because it tells us how likely a player is to avoid making outs! An average player will have an OBP of around .350.

Slugging Percentage (SLG) is a basic measure of a player's power. It is calculated by dividing the number of total bases a player hits for (one base for a single, two bases for a double, etc.) by their number of at bats; the average is about .450. We can combine OBP and SLG into a great statistic called On Base Plus Slugging (OPS), which is one of the best simple statistics to look at when evaluating a hitter. About .800 is average; league leaders are usually over 1.000.

When it comes to pitchers, Walks Plus Hits Divided by Innings Pitched - or the much easier to digest WHIP - is probably the most important non-traditional statistic you can know. It's simple to calculate - simply add a pitchers walks and hits allowed, then divide by innings pitched - and gives a good indication of how effective a pitcher has been. The average WHIP is around 1.30.

Advanced Statistics

Even strict traditionalists can see the value in OBP or WHIP; they simply take the statistics we already know and love, and package them in better ways. However, mention some of the following stats in the wrong crowd, and you might get some strange looks!

Value Over Replacement Player (VORP) is a statistic that attempts to tell us how many more runs a player is worth than a hypothetical "replacement player," or a typical player who could be called up from the minors to fill in at the same position as the player being looked at. It is available for hitters and pitchers, but doesn't factor in fielding ability. According to Baseball Prospectus, on June 28, 2007, Alex Rodriguez currently has this season's highest VORP for position players at 54.7; Dan Haren leads all pitchers at 44.6.

VORP can be further refined into Wins Above Replacement Player (WARP). WARP includes fielding in the calculations, using VORP along with other statistics to estimate exactly how many wins each player is worth over a replacement player.

These statistics are among the most commonly cited in discussions about Sabermetrics or the true value of baseball players, and are definitely worth knowing. Having an idea of what they mean should help make sense of most statistical acronyms you're likely to encounter, and will certainly better help you evaluate your favorite players' performances.