ERA, or Earned Run Average for those of us out there who have too many acronyms and abbreviations to sort through in our everyday lives, has been around since the 1900s.

That means that pitchers who are good at preventing earned runs are also generally good at preventing unearned runs. Of the top 50 pitchers in career (normalized) ERA, 46 of them were better than ...

Therefore, to determine which player is the most skilled, we need to find statistics that better isolate a pitcher's performance. One such stat is Skills-Interactive Earned Run Average (SIERA).