True Runs Allowed (tERA) is a defense-independent ERA estimator built by Graham MacAree from StatCorner that was designed as an alternative to FIP and xFIP. The most common complaint about FIP and xFIP is that they completely ignore performance on balls in play, while batted balls can still tell us something about a pitcher’s skill level: groundballs are good (since they normally result in outs), flyballs have a higher probability of resulting in extra basehits, pop-ups are almost guaranteed outs, and line drives are the most likely type of ball in play to end up as a hit.
tERA includes all of these variables, and is based on the same scale as ERA, FIP, and xFIP. It is a little less accurate in predicting future performance than xFIP, but it is still more valuable than ERA and provides us with another lens through which to evaluate pitchers.
Now that SIERA is carried at FanGraphs, tERA is somewhat redundant. SIERA also includes batted ball information, and does so in a way that makes it a more accurate and predictive ERA estimator than tERA (albeit slightly). That’s not to say that tERA doesn’t have its uses, but if you have to pick one, use SIERA.
Please note that the following chart is meant as an estimate, and that league-average tERA varies on a year-by-year basis. To see the league-average tERA for every year from 2002 to the present, check the FanGraphs leaderboards.
Things to Remember:
● The original form of this statistic is tRA, which is calculated on a Runs Allowed scale as opposed to an Earned Runs Allowed scale. This makes tRA less easy to compare with ERA, FIP, and xFIP, but some analysts still prefer this style because it excludes the subjectivity inherent in Earned and Unearned runs. You can find tRA available over at StatCorner.
● Also at StatCorner, you can find tRA*, which is a regressed version of tRA. It uses a player’s past performance and league-average rates to predict how a player should perform in the future. It may listed in some locations as tRAr.
● Batted ball classifications should not be treated as 100% accurate, since they rely upon a human scorer saying, “Yes, that looks like a line drive and not a fly ball.” This is a small caveat to keep in mind when using tERA or any statistics that rely on batted ball data.
Links for Further Reading: