Regular contributor Patriot makes his SDR debut with a column about OPS.

To many in the general population of baseball fans, the singular metric associated with sabermetrics might be On Base Plus Slugging (OPS).  OPS has gained a measure of acceptance in the mainstream as an offensive metric in both its raw form and the park- and league-adjusted variant OPS+, and given the long history of their use in sabermetrics (both having been developed by pioneering sabermetrician Pete Palmer), it is no surprise that the metrics are associated with the field and are still in common use.  However, OPS has shortcomings that can be problematic for serious application:

OPS could be improved by weighting OBA more heavily; studies have suggested a multiplier in the neighborhood of 1.8 to maximize correlation with team runs scored (i.e., OBA*1.8 + SLG).  Doing so, though, would take away one of the strongest selling points of the metric, which is ease of calculation.

The lack of a 1:1 relationship with runs scored does not mean that OPS has no validity as a metric, but it does make it more difficult to interpret what various OPS values mean in terms of measuring offensive output.

(H + BB + HBP)/(AB + BB + HBP + SF) + TB/AB

If presented with this formula and you were previously unfamiliar with OBA and SLG as separate measures, you might ask, “Why are walks and hit batters divided over one denominator (plate appearances) while total bases are divided by another (at bats)?”  The use of different denominators requires more involved analysis to understand the relative weights that OPS places on each offensive event.

OPS would have never been created without OBA and SLG already existing.  OPS is easy to calculate, but only if one presumes that OBA and SLG have already been calculated; if not, OPS is not much quicker to calculate than alternative metrics.

100*(OBA/league OBA + SLG/league SLG – 1)

OPS+ is actually the sum of relative OBA and relative SLG rather than a relative version of the combined total.  Some have criticized the name of the statistic as misleading because other “plus” statistics (e.g., ERA+) are a simple quotient of the player’s figure and the league average.  However, there are two major benefits reaped by the way OPS+ is figured.  One is that it implicitly weighs OBA more heavily than simple OPS, as the league SLG is typically 20-30% higher than league OBA.  Additionally, OPS+ has a 1:1 relationship with runs scored, so a team with an OPS+ of 110 should score about 10% more runs than average.

While these are nice properties, many of the other shortcomings of OPS are not rectified.  The higher weight on OBA still leaves room for improvement in correlation with team runs scored, and the specific variant of OPS+ most widely disseminated utilizes a complicated and questionable park adjustment methodology.

The message here is not that OPS should never be used or that it is not an improvement on starting with a batter’s triple crown stats. But when serious analysis or a nuanced evaluation is in order, OPS leaves much to be desired.

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