There can sometimes be a huge gap between a pitcher's ERA and FIP, leading to different thoughts as to how they actually performed in any given year. How do we know which one is the more accurate number?
Evaluating starting pitchers is a tricky business. There is a metric ton of metrics out there to consider, and sometimes those numbers contradict each another.
If one is going to quantify the value of a pitcher, there are a few numbers analysts use most frequently. Batted-ball data, strikeouts and walks, velocity, and the movement of breaking pitches are all vital components in deciding just how good a pitcher has been.