FIP Challenge Results Part I
Back at the All-Star break, I wrote a piece here asking Should Fantasy Owners Use FIP? I included a chart of all of the starting pitchers who had a difference of 0.50 or greater between their FIP and xFIP.
The article ended with a promise to follow up and see which metric did better in predicting pitchers ERA in the second half of the season. Here is the table from the original article, with one additional column, this one the pitcher ERA in the second half of the season.
| Name | HR/FB | ERA | FIP | xFIP | 2nd Half ERA |
|---|---|---|---|---|---|
| Greinke | 3.1 | 2.12 | 1.97 | 3.13 | 2.21 |
| Pineiro | 3.5 | 3.20 | 2.99 | 3.77 | 3.83 |
| Lincecum | 3.9 | 2.33 | 2.01 | 2.78 | 2.67 |
| Braden | 4.6 | 3.12 | 3.40 | 4.62 | 7.40 |
| Maholm | 4.6 | 4.60 | 3.55 | 4.40 | 4.24 |
| Wakefield | 4.9 | 4.31 | 4.17 | 5.50 | 6.00 |
| Kershaw | 5.0 | 3.16 | 3.54 | 4.28 | 2.27 |
| Lowe | 5.5 | 4.39 | 3.74 | 4.38 | 5.05 |
| Lee | 5.7 | 3.47 | 3.27 | 4.13 | 2.92 |
| Zambrano | 5.8 | 3.53 | 3.79 | 4.55 | 4.14 |
| Jurrjens | 5.9 | 2.91 | 3.82 | 4.62 | 2.24 |
| Niemann | 6.2 | 3.73 | 4.47 | 5.49 | 4.15 |
| Blackburn | 6.2 | 3.06 | 3.97 | 4.90 | 5.47 |
| E. Jackson | 6.4 | 2.52 | 3.45 | 4.34 | 5.07 |
| Pelfrey | 6.5 | 4.47 | 4.01 | 4.51 | 5.67 |
| Garland | 7.4 | 4.53 | 4.60 | 5.13 | 3.42 |
| F. Hernandez | 7.4 | 2.53 | 2.95 | 3.47 | 2.43 |
| Verlander | 7.5 | 3.38 | 2.70 | 3.23 | 3.52 |
| Bannister | 7.5 | 3.66 | 3.93 | 4.46 | 6.63 |
| Sabathia | 7.5 | 3.86 | 3.73 | 4.29 | 3.53 |
| Penny | 7.55 | 4.71 | 4.19 | 4.97 | 5.08 |
| Padilla | 7.5 | 4.53 | 4.53 | 5.13 | 4.58 |
| Washburn | 8.0 | 2.96 | 3.88 | 4.46 | 5.23 |
| Weaver | 8.0 | 3.22 | 3.80 | 4.47 | 4.47 |
| Blanton | 15.3 | 4.44 | 4.74 | 4.00 | 3.62 |
| Arroyo | 15.3 | 5.38 | 5.68 | 4.99 | 2.24 |
| Moyer | 15.4 | 5.99 | 5.84 | 5.06 | 3.48 |
| Cahill | 16.1 | 4.67 | 5.83 | 5.18 | 4.59 |
| Volstad | 16.2 | 4.44 | 4.58 | 3.95 | 6.79 |
| Porcello | 17.8 | 4.14 | 5.03 | 4.41 | 3.92 |
| Looper | 17.9 | 4.94 | 5.71 | 4.65 | 5.54 |
| Geer | 18.5 | 5.79 | 5.87 | 4.61 | 7.07 |
| Harden | 18.6 | 5.47 | 5.17 | 3.91 | 2.55 |
| R. Johnson | 18.9 | 4.81 | 4.92 | 3.83 | 8.10 |
There are 34 pitchers in the above chart. On a raw scale, the xFIP metric did a better job of predicting 2nd half ERA, coming closer than FIP on 20 of our pitchers. Furthermore, xFIP did a better job of forecasting 14 of the 24 players with low HR/FB rates and did a better job forecasting six of the 10 players with high HR/FB rates.
In the original article, I projected the two systems would be fairly close to 50-50, so xFIP slightly exceeded my expectations (59-41). But what really surprised me was how few players’ 2nd half ERA fell in between the range of their first half FIP and xFIP. For example, Pineiro had a 2.99 FIP and a 3.77 xFIP and his second half ERA was 3.83, outside the range of the two systems. Only six of the 34 pitchers had 2nd half ERAs inside the range. Both FIP and xFIP correctly forecasted three of those pitchers.
Later today I will post a breakdown of all 34 pitchers in this survey.
shouldn’t you just look at whether the 2nd half hr/fb rate regressed closer to 11% expected by xfip or stayed closer to the 1st half hr/fb rate? the way you are doing it does not take into account whether things like k/bb improved or worsened. what should be measured is whether 2nd half FIP came closer to first half FIP or 1st half xFIP. or am i wrong? this is just me trying to make sense of the methodology.