THE BOOK--Playing The Percentages In Baseball

Wednesday, May 19, 2010

Reader mail of the day: FIP v ERA

Hi,

I’m not exactly a stat-savvy baseball fan, but I enjoy reading your blog. I have a probably simple question to ask but I didn’t know of anyone else I could ask who would answer me.

Basically: If you figured out the total xFIP of a team and subtracted it from the team’s actual RA/9, would that give you a good sense of how a team’s defense is doing? It seems quick and dirty but I don’t see why it wouldn’t give a good overall picture of team defenses.

Thanks for your time,

The difference between FIP and RA/9 is that RA/9 includes these four things:
1. Team fielding
2. Pitching talent on balls in play
3. Sequencing of events (i.e., performance with men on base)
4. Park factors (different park factors also applies to FIP)

So, it would be inappropriate to think #1 alone is the cause.