Everyone seems to argue that ERA is biased in favor of pitchers with good defenses, and while that is true, it is still the best way to measure the quality of a pitcher; at least a starting pitcher. I will argue that for a relief pitcher, WHIP is more important since you often want a guy that can get out of a situational jam (IE: Bases loaded, 1 out), but I digress.
As most of you know, FIP stands for "Fielding Independent Pitching," and is a variation of sabermetrics. The formula is as follows: FIP = (13 HR + 3 BB - 2 K) / IP) + 3.1.
This formula FAILS because it implies that all successful contact pitchers are lucky. It can take a great pitch to jam a good hitter into hitting a pop up infield deep, and it can take a great pitch to have a good hitter tap a routine ground ball. None of these are rewarded with this formula.
You can make bad pitches which go for screaming line drives, doubles/triples off the wall, ground balls up the middle, etc. All of which even a good defense wouldn't save you from. None of these are penalized with this formula.
It doesn't take a baseball genius to see that this formula rewards pitchers that pitch for strikeouts and avoid homeruns. The pitcher that pitches for contact is screwed. The pitcher that gives up a lot of base hits, gets a lot of strikeouts, and avoids homeruns benefits. I'm not saying ERA is perfect. I'm just saying it's better than this garbage formula which has several biases of its own.
It only took me one attempt to think of a pitcher that could disprove this formula. James Shields of the Tampa Bay Rays. I'm sure everyone here agrees; the Rays have one of, if not the best defense in the league. Despite giving up a lot of homeruns, James Shields gives up very few walks and has a lot of strikeouts. His FIP is 4.099 while his ERA is 4.79. I guess the Rays' terrible defense has really let him down.
And don't get me started on why contact pitchers are better than strikeout pitchers. That's a whole different argument.