FIP/ERA

I use FIP quite a bit. It's a theoretical ERA from Hardball Times which uses a pitcher's peripheral statistics (namely K/9, BB/9 and HR/9) to extract the effects of defense on a pitcher's performance record (ERA) theoretically giving a better picture of what a pitcher contributes by virtue of his own skills.

For it to be of any use, it needs to be predictive. It needs to show us that something happening now is or isn't likely to happen again in the future. So what I did was to compare 2005 ERA and 2005 FIP to 2006 ERA in order to determine whether ERA or FIP correlated better year to year.

I looked at the 51 pitchers from 2005-2006 who pitched 150+ innings in the same league in both 2005 and 2006

;<

          05 FIP  05 ERA 06 ERA
J Santana 2.80   2.87  2.77
Haren     3.84   3.73  4.12
Zito      4.37   3.86  3.83
Lackey    3.08   3.44  3.56
Garcia    4.05   3.87  4.53
Millwood  3.75   2.86  4.52
Bonderman 3.92   4.57  4.08
Westbrook 3.94   4.49  4.17
Garland   4.22   3.48  4.51
Robertson 4.72   4.48  3.84
Johnson   3.77   3.79  5.00
Rogers    4.07   3.46  3.84
Buerhle   4.37   3.86  4.99
Lee       3.80   3.79  4.40
Mussina   4.03   4.41  3.51
Contreras 4.20   3.61  4.27
Blanton   4.40   3.53  4.82
Sabathia  3.70   4.03  3.22
Lopez     4.64   4.90  5.90
Washburn  4.37   3.20  4.67
Meche     5.04   5.09  4.48
Silva     4.17   3.44  5.94
Byrd      3.94   3.74  4.88
Pineiro   4.41   5.62  6.36
Radke     4.45   4.04  4.32
Moyer     4.39   4.28  4.39
Webb      3.42   3.54  3.10
Harang    3.59   3.83  3.76
Smoltz    3.14   3.06  3.49
Willis    2.91   2.63  3.87
Carpenter 2.86   2.83  3.09
Capuano   4.54   3.99  4.03
Oswalt    3.08   2.94  2.98
Hudson    4.22   3.52  4.86
Lowe      4.10   3.61  3.63
Pettitte  3.03   2.39  4.20
Zambrano  3.62   3.26  3.41
Schmidt   3.77   4.40  3.59
Morris    3.91   4.11  4.98
Davis     3.87   4.16  4.91
Peavy     2.80   2.88  4.00
Francis   4.62   5.68  4.16
Myers     3.99   3.72  3.91
Glavine   3.56   3.53  3.82
Marquis   4.88   4.13  6.02
Suppan    4.48   3.57  4.12
Penny     3.57   3.90  4.33
Fogg      4.90   5.05  5.49
Lieber    4.13   4.20  4.93
Ja Wright 5.08   5.46  5.48
Milton    5.37   6.47  5.54

R for FIP = 0.64
R for ERA = 0.51

(R is correlation coefficient)