Know Your Stats: OPS/OPS+

For the next few days, I will be bringing back my “Know Your Stats” series that I began a few years back to highlight some important sabermetric stats and concepts. We begin this afternoon with OPS and OPS+.

OPS, or On Base Plus Slugging was one of the first sabermetric stats to go mainstream. It is, as the name implies, On-Base Percentage plus Slugging Percentage. It’s crude and simple, but it’s a good quick and dirty reference tool

OPS is expanded on even further when made into an index, OPS+. OPS+ does something very important: puts the OPS into context. The stat makes it possible to compare players from different eras, different teams, and different ballparks.

OPS+ is set on a percentage point scale. Essentially it is the percentage of league OPS. 100 (or 100% of the league average) is the league average, while a 110 mark is ten percent better than league average, and 90 is ten percent worse.

There are many issues with the crude OPS and OPS+. Is one point of OBP worth the same as one point of SLG? The math says no. In fact, the math says a point of OBP is worth 1.7 times what a point of Slugging is. Neither OPS nor OPS+ tell you the composition of OBP or Slugging and thus overvalues extra base hits.

OPS as I mentioned, is crude and the most basic sabermetric stat out there. It has its flaws, but it is a great way to get people to start thinking about sabermetrics. OPS and OPS+ are solid stats and certainly better than batting average, although not as good as wOBA or wRC+.

More thoughts

Anytime there is a stat with a “+” at the end, that means it is an index and adjusted for park factors. I get a lot of questions and concerns about the fact that these park factors sometimes change from year to year. However, these changes are so miniscule from year to year that they don’t really effect the stat. Here are Yankee Stadium’s park factors going back to 2009: