OPS, OPS+, and wOBA

We already went over on-base percentage and its advantages over batting average, but as I said on-base percentage tells a better story but not the whole story. On-base plus slugging (OPS) helps add to the book. It is just as it sounds, your on-base percentage plus your slugging percentage. Most people who really get into the stat weeds are not big fans of OPS, as it gives the same value to the two. In reality being on base is about twice as important to run scoring as slugging.

There is an OPS stat that you won’t find on Fangraphs or any of the baseball cards in your attic or garage, OPS+. OPS+ gained traction on Baseball-Reference.com. It is more informative than OPS because it normalizes all park factors and other small OPS outliers. The way to read OPS+ is also much easier, as it is normalized to 100. So instead of trying to figure out exactly where on the scale a guys .882 OPS falls you just have to look at a number and you’ll have your answer. Since it is based on a scale where the average is 100 a guy with a 200 OPS+ like Mike Trout had last season means Trout is 100% better than average. He also gains no boost or no penalty for the park where he plays, Coors field comes to mind. Nolan Arenado had a .935 OPS in 2018, playing all his home games in the thin air of Denver if you use OPS + his league and home park are all taken into account. His OPS+ in 2018 was 133, meaning simply he was 33% better than average in any park, in any era.

Instead of using OPS though I prefer to use a weighted on-base average (wOBA). In OPS all hits are created equally, which we know they are not. That’s where we come in, its used to measure a hitter’s overall offensive value, based on the relative values of each distinct offensive event. Weighted On-Base Average combines all the different aspects of hitting into one stat, weighting each of them in proportion to their actual run value. I won’t get too far into the weeds but if you would like to see what the weights are for each year here. For example, you would take player x season home run total by 2.031 to figure out that portion of the formula, but enough of that.

One of the beauties of wOBA is that it is extremely easy to use once you learn the basics. League average wOBA is always scaled to league average OBP, so if you know what a good OBP is, you know what a good wOBA is. An average wOBA is .320, .290 is considered awful, and .400 is excellent. As you can see, the rule of them looking at this stat is very similar to what you would expect from OBP. wOBA on FanGraphs is not adjusted for park effects, meaning that batters that play in hitter-friendly parks will have slightly inflated wOBAs. Also, this stat is context-neutral, meaning it does not take into account if there were runners on base for a player’s hit or if it was a close game at the time, there is my favorite offensive stat for that.

Thanks as always for reading and we will be running these pieces all week for what we are calling advanced stat week. Let us know what you would like to see me tackle or if you have any questions. You can ask or just follow us on twitter @SidedSox, and follow us on Facebook. You can also email us at SoxSided@Gmail.com.

Mort

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