Advanced Stats 101: ERA+ and OPS+

sabermetrics
In the last installment, we dug into WAR andBAbip, two commonly used stats by many writers and fans. Today we are going a little further into the advanced stats category with ERA+ and OPS+. Unlike WAR, these two stats actually give you a baseline for “average”, or the starting point of “zero” when comparing players. Both stats are widely used, and they are two of the favorites at SDI. If you follow any of us on Twitter during the season, you’ll see both mentioned quite a bit. Let’s dive in.
ERA+ (Earned Run Average, Ballpark Adjusted)
We are going to start by explaining ERA. ERA is the average amount of earned runs a pitcher gives up over 9 innings (which I assume that most, if not all of you know). It is calculated by the following equation:

(9 * ER / IP). Its a simple stat, that has been around for many years, and has widely been accepted as “the” stat when judging pitching. What it does not do, however, is take into account the effect a ballpark has on a pitcher’s performance, or give us an average. For example, if Colby Lewis faced the Mariners in Wrigley Field and then pitched the same game against the same team in Dodger Stadium at night, would the outcomes be the same? Probably not. That’s a hypothetical, obviously since Colby could not duplicate the exact same pitches and the hitters would react differently, but you get the idea. What ERA+ does, is to average the ERA of a player against the league to give us the “average” pitcher. The equation is this: 100*(league ERA/the player’s ERA). What does this mean? It means that the “average” pitcher will have an ERA+ of exactly 100. ERA+ gives us a baseline or starting point to measure a pitcher against the league. Lets look at Derek Holland to give you a better idea.
. Derek Holland Games Innings Hits Earned Runs ERA ERA+
. 2011 32 198 201 87 3.95 112
. 2012 29 175.1 162 91 4.67 97
By looking at Holland’s ERA+ he was an above average pitcher in 2011, and slightly below average in 2012. This statistical category is a tremendous tool to look at a player compared to what the rest of the league is doing as far as ERA goes. Again, this is not the overall judge of a pitcher, but a way to help gauge a player against the rest of the league. Just remember, ERA+ is not a complete picture of a performance of a player. There are many factors to be considered such as holding runners, base stealing, etc.

OPS+ (On Base plus Slugging, Ballpark Adjusted)
OPS+ works much the same way as ERA+, but for hitters. It gives us a starting point to judge a player, by giving us the average. Let’s start with a quick tutorial of OPS. It’s on base percentage plus slugging percentage. That’s it, pretty simple. Any hitter with an OPS above .900 would be put into the “great” category. The OPS+ formula is:100*[OBP/lg OBP + SLG/lg SLG – 1]. The same with ERA+, 100 is the league average, and that is our “zero” point for looking at a player’s performance. Again, we’ll show you a player’s stats to help you get an idea. Here’s Adrian Beltre:

. Adrian Beltre AVG TB OBP SLG OPS OPS+
. 2009 (SEA) .265 170 .304 .379 .683 83
. 2012 (TEX) .321 339 .359 .561 .921 137
I picked two very different years in the career of Beltre, to show you both ends of the spectrum. Adrian in 2009 only played in 111 games, however in those games he was a below average hitter. Last year for the Rangers he was above average. Beltre’s 137 OPS+ in 2012 is a great year, and an excellent way to look at his year from an on base and total base (compared to the average of each individual year). Once again, these stats are not stand alone stats. They should be used in conjunction with others. Taking Beltre’s 137 OPS+ and combining it with his 6.7 WAR from 2012, the picture starts to develop for what kind of a year 2012 was for him. Obviously we could look at batting average, home runs and RBI’s and get a similar result, but using OPS+ and WAR (plus others) we get an idea of his 2012 compared to the rest of the league without digging through stat after stat to compare. It’s wrapped up in a bow for us. Again, we hope this helps you understand advanced stats a little more than you did prior to reading this.

Next week, Advanced Stats 102. It will be all about pitching with RAR, FIP,xFIP, and my personal favorite Gsc.

Patrick Despain is the CEO and Co-Founder of ShutDown Inning. He can be reached at Patrick.Despain@shutdowninning.com or on Twitter @ShutDownInning
Patrick Despain
Patrick is a member of the IBWAA and creator of Shutdown Inning. He was raised him Arlington, Texas and grew up watching games on HSE and listening to Eric Nadel and Mark Holtz on the radio. He is a long time Rangers fan and never achieved his dream of being a bat boy. He know lives in Georgia with dreams of a Texas return.

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