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 ERA- and ERA+.

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ERA+ is an advanced baseball statistic in which a pitcher’s ERA is adjusted to both the pitcher’s ballpark as well as the league-average ERA for a given season. Average ERA+ is scaled to 100, thus any pitcher with an ERA+ over 100 is considered above average, and any below 100 is considered below average. The idea behind ERA+ is to better understand a pitcher’s ERA as it relates to other pitchers in the league and the stadiums in which they play.

ERA- works very similarly to ERA+. ERA-, however, is scaled differently, with numbers below 100 representing a higher quality pitcher than those above 100. Also with ERA-, each point above or below 100 represents a percentage point. Thus a pitcher with an ERA- of 80 will be 20% better than the league average of 100.

While ERA+ was created first, ERA- is usually considered more reliable and telling of a pitcher’s value and is becoming more commonly used. It also helps that ERA- is scaled by percentage points, giving a clearer view and a shorter range of numbers to deal with.

ERA+ and ERA- are valuable stats when making sense of results versus quality of pitching. While an average pitcher can show you a good ERA while playing in a cavernous stadium such as AT&T Park in San Francisco, that pitcher will likely be exposed by ERA- greater than 100. Likewise, a quality pitcher seemingly at league average may have an ERA- of less than 100 while playing in a hitter’s haven such as Oriole Park or Coors Field. At the very least, ERA+ and ERA- can help fantasy owners sift through mid-range pitchers and determine a more finite value for them. This stat can be incredibly useful at the end of fantasy drafts and when players change teams mid-season and can be more indicative of future performance than regular ERA.

Roy Widrig is a correspondent at FantasyPros. To read more from Roy , check out his archive and follow him @rolewiii.