Definition of OPS in Baseball
Definition 1
The sum of On-base Percentage (OBP) and Slugging Percentage (SLG) is known as OPS. $$ OPS := OBP + SLG $$
Description
A high on-base percentage has been considered to increase the expected score for the team, and a high slugging percentage is seen as an indicator of the ability to realize these expectations. The argument that batting average has become worthless as a quantitative record in modern baseball has been accepted as a theory, and the front offices have started to take interest in metrics that actually lead to scoring.
But, do we really need to know which one, on-base percentage or slugging percentage, is more important? There are occasionally players who have an abnormally high value in one, but as the saying Good Baseball summarizes, generally, good players perform well in baseball. Of course, the context of “good baseball” mentioned here and the one being discussed now are different, but in any case, outstanding players usually have exceptional records in all aspects without necessarily looking at their metrics.
In this sense, OPS is advantageous as it is simple to calculate and effectively summarizes a player’s value. As it uses an English acronym, it might appear unfamiliar at first to those new to baseball, but in reality, it’s such a simple measure that it might be somewhat embarrassing to call it sabermetrics.
A high OPS for a batter means that, whether through getting on base or hitting for extra bases, they significantly contribute to scoring. If one of these is low, but the OPS is high, that itself is remarkable. It means that the player is exceptionally good in the other aspect to compensate for lacking in one.
The only case when a player has a high OPS but low performance is if they are an outlier who only has a high batting average but cannot draw walks or hit for power. This happens because both on-base percentage and slugging percentage formulas inherently include batting average. Yet, as this still means an abnormally high batting average, it cannot be completely dismissed.
Sabermetrics
From an analyst’s perspective, OPS has no meaning. Or rather, it’s not that it has no meaning, but since it decomposes into on-base percentage and slugging percentage, there’s no reason to summarize them into OPS. If one were to analyze using on-base percentage, slugging percentage, and OPS as independent variables, they would form a perfect linear dependence.
If OPS has any significance in sabermetrics, it would likely be when OPS itself is the dependent variable. Since OPS effectively summarizes a batter’s performance, predicting OPS could be a goal in itself. Of course, if on-base percentage and slugging percentage are used as independent variables in this case, it would be too trivial, and there should be an effort to explain OPS with other variables.