Beginner’s Guide to Sabermetrics: OPS

FantasyPros has put together a glossary of sabermetrics statistics for readers to reference. Deeper statistical analysis is being used by fantasy players more and more in daily and season-long leagues. We’re providing the glossary so that you can easily reference what the stats we use in our articles refer to and how they should be used for fantasy baseball purposes. Below we’ll take a look at OPS.

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OPS stands for On-Base Plus Slugging, and is really just that. It is the player’s on-base percentage added to his slugging percentage. So, in order to really break down OPS, we must first break down its parts. On-base percentage, or OBP, is becoming more and more important in baseball. While a hitter’s batting average can certainly tell a story, it is a very flawed story that ends half way through the narrative. On-base percentage is able to fill those gaps, crediting hitters who are able to take walks and punishing those who swing at everything. The formula to determine a batter’s on-base percentage is a bit intimidating to look at, but actually quite simple. The formula is as follows:

OBP = (H + BB + HBP) / (AB + BB + HBP + SF)

In the formula, H stands for hits, BB for base on balls or walks, HBP for hit by pitch, AB for at bats, and SF for sacrifice flies. Basically, OBP is calculated by dividing the amount of times a batter got on base by the times that batter could have gotten on base (with the added sac fly aspect). Regarding sac flies, they were not uniquely counted in OBP calculations before 1954. Up until then, sac flies were part of SH, or sacrifice hits, which also included sacrifice bunts. From 1954 onward, sac bunts are no longer counted against batters in terms of OBP, since it is a call usually given by the manager and not representative of the batter’s ability to reach base.

After calculation, OBP gives a number much like batting average: .300, .350, .400 and such. This can be seen as a strict percentage as well. A batter with a .400 on-base percentage reaches base in 40% of his plate appearances (after eliminating sac bunts).

The other part of OPS, slugging percentage, can be a slightly more complicated statistic to calculate, but perhaps just as useful. Slugging percentage helps to calculate a hitter’s power in that it weighs hits higher based on bases earned. The basic formula for slugging percentage is:

SLG = TB / AB

In that formula, TB stands for total bases, and AB for at bats. The longer formula for finding slugging percentage boils down to the same as total bases divided by at bats, but looks a lot more complex:

SLG = [(1B) + (2 x 2B) + (3 x 3B) + (4 x HR)] / AB

Here, 1B is singles, 2B is doubles, 3B is triples, and HR is home runs. The stat Total Bases provides one base for a single, two for a double, three for a triple, and four for a home run, so it works out to be much easier to calculate as long as TB numbers are available.

The benefit of slugging percentage is that a batter who hits 50 doubles is more productive than one who hits 50 singles. It ends up being a general power statistic, although triples, based more on speed and luck, can sometimes throw a bit of a wrench into calculations. In theory, the highest possible slugging percentage is 4.000, given a batter only ever hitting home runs in every career at-bat. Slugging is not a perfect statistic, but it is certainly useful.

So, now that its two parts, OBP and SLG are covered, let’s talk OPS. OPS was originally simply called “Production” by Bill James. “Production” should tell you just how crucial OPS can be when looking at a player’s offensive numbers. Like most statistics, it is not fool proof, but generally OPS works well in determining a player’s offensive value to a team. The main issue with OPS as a statistic is that it weighs its two parts equally. Research has shown that OBP is in fact almost twice as important (1.8 times, to be exact) as SLG in scoring runs. However, since OPS is the most easily accessible composite stat, it remains a useful one throughout baseball. It is the only easily understood statistic that encompasses contact, plate discipline, and power.

In terms of judging players by their OPS, there are some generally accepted numbers that allow a range from excellent to awful. The chart below comes from Fangraphs and shows a quick reference on judging OPS:

This chart is a rough rating system, as OPS can vary greatly based on home ballpark, and year-to-year differences can be quite great. Also, a middle infielder with an OPS equal to that of a first baseman is likely more valuable to his team because of positional scarcity. The general rule of thumb, however, is that an OPS of .800 is good. Anything higher is particularly impressive, while anything below is not.

The record for single-season OPS belongs to Barry Bonds, whose OPS in 2004 was a ridiculous 1.4217. In fact, Bonds appears on the top-10 single season OPS chart four times, including the top two spots. Also in the top-10 are Babe Ruth (four times) and Ted Williams (twice). The career OPS leader board has Babe Ruth on top with a 1.1636 OPS. Filling out the top-five of best career OPS are Ted Williams (1.1155), Lou Gehrig (1.0798), Barry Bonds (1.0512), and Jimmie Foxx (1.0376).

OPS is already used as its own statistic in some deeper and custom fantasy leagues, but it can be quite useful even in those leagues where it is not counted. A player with a high OPS will certainly be more “productive” than one with a lower one. The more often a batter gets on base, the more often he will be able to score runs. Likewise, the more power potential in a player’s bat, the more likely he is to contribute in classic categories like home runs and RBI.

David A Marcillo is a correspondent at FantasyPros. To read more from David, check out his archive and follow him @DavidMarcillo77.