Who’s up and who’s down? Which pitcher will improve upon a stellar season, and who is headed for the trash heap? SIERA and xFIP attempt to answer these questions from year to year, but they’re not totally interchangeable metrics. Why? The biggest difference is the way each uses strikeout rates.
That’s not to say that the two statistics don’t generally say the same thing. In fact, they’re much more reliable – and calculated much differently – than traditional ERA. For a quick example, take a look at the top 10 pitchers in all three metrics during the past four seasons.