Fielding Independent Pitching
ERA built only from what the pitcher controls: strikeouts, walks, home runs.
What it actually is. Fielding independent pitching: an earned run average built only from strikeouts, walks, hit batters and home runs, the four outcomes the defense cannot touch, scaled to look like an earned run average.
What a scout reads off it. When earned run average and this disagree, the gap is the defense, the park and the sequencing. Over a full season the gap is usually the more informative thing on the page: it tells you which direction the results are going to move.
How it lies to you. It assumes every pitcher has average control over what happens to balls in play. A few do not, and pitchers who force weak contact are systematically undersold by it, which is what SIERA was built to fix.
Batter's Eye: look up anything in baseball