As many of you already know, Fantistics uses sabermetric theories to create it's player projections model. These theories are the foundation to our successful forecasting history. One of my favorite forecasting models that we monitor here at Fantistics is Expected ERA.
Expected ERA (XERA) depicts a pitcher’s "True ERA" as it bases its expectation on factors within a pitcher's control. These factors include Hits, Walks, Home Runs allowed and K’s. When you consider the inequity with the ERA calculation, specifically related to errors and base runners inherited/left, many including myself consider XERA to be a more precise gauge of ability.
Expected ERA is a term coined by two Sabermetric researchers (Gill and Reeve) who developed the following mathematical formula ((.575 * H/9 ) + (.94 * HR/9 ) + (.28 * BB/9 ) - (.01 * K/9 ) - Normalizing Factor). The normalizing factor is based on the league (typically in the .270 and .285 range)
The best way to use XERA is to compare it to the actual ERA. Using the delta between the two indicators we can make observations as to whether the pitcher’s ERA was a true gauge of his ability for the given period.
Overall, based on the MLB starting pitching universe, XERA and ERA usually are almost identical as a whole. On average, for the top 150 pitchers, both hover around 4.00.
Pitchers with a lower ERA than Expected
When I wrote this
piece last
year, I identified 4 pitchers whose 2006 ERA was well below their
expected ERA. I went on to say that Woody Willaims, Nate Robinson,
Bronson Arroyo, and Justin Verlander
Here are the pitchers who had a lower than deserved ERA in 2007:
| Lower ERA than Deserved | ||||
| Player | XERA | ERA | ERA Diff | Notes |
| Thompson,B. | 5.76 | 4.73 | (1.03) |
Using the similar criteria as mentioned above: Not including pitchers
who did not improve their ERA in 2006 (black), and also removing the
pitchers who have little significance from a fantasy standpoint; We
can isolate the pitchers who are "due" for a major rise in ERA this
year.
Dan Haren - sure the more to the NL should provide him with an edge, but his '07 ERA of 3.07 was almost 60 points less than what it should have been. John Lackey had a banner season in '07, but his runner stranded percentage of .77 had him skating on thin ice. His expected ERA last year should have been in the 3.50 zone. Mark Buehrle always worries us, as do many other low K/I ratio pitchers. Having the balls hit into play more often increases the probability of failure. Couple this with the rise in his FB/GB ratio. Even before the health issues sidelined Kasmir this spring, we were projecting a downturn. Kaz ERA should have been closer to 4 last year. |
| Hernandez,L. | 5.83 | 4.93 | (0.89) | |
| James,C. | 5.01 | 4.24 | (0.77) | |
| Davis,D. | 4.99 | 4.25 | (0.74) | |
| Chico,M. | 5.28 | 4.63 | (0.65) | |
| Oswalt,R. | 3.83 | 3.18 | (0.65) | |
| Hernandez,F. | 4.42 | 3.78 | (0.64) | |
| Haren,D. | 3.66 | 3.07 | (0.59) | |
| Olsen,S. | 6.38 | 5.81 | (0.58) | |
| Weaver,J. | 4.48 | 3.91 | (0.57) | |
| Schilling,C. | 4.39 | 3.87 | (0.51) | |
| Arroyo,B. | 4.74 | 4.23 | (0.51) | |
| Sampson,C. | 5.07 | 4.59 | (0.49) | |
| Kendrick,K. | 4.35 | 3.87 | (0.48) | |
| Lowry,N. | 4.38 | 3.92 | (0.45) | |
| Lackey,J. | 3.51 | 3.05 | (0.45) | |
| Vargas,C. | 5.51 | 5.09 | (0.42) | |
| Billingsley,C. | 3.72 | 3.31 | (0.41) | |
| Byrd,P. | 5.23 | 4.82 | (0.41) | |
| Buehrle,M. | 4.02 | 3.63 | (0.40) | |
| Gorzelanny,T. | 4.27 | 3.88 | (0.38) | |
| Batista,M. | 4.67 | 4.29 | (0.38) | |
| Kazmir,S. | 3.86 | 3.48 | (0.37) | |
| Fogg,J. | 5.31 | 4.94 | (0.37) | |
| Penny,B. | 3.37 | 3.03 | (0.34) | |
| Wainwright,A. | 4.02 | 3.70 | (0.32) | |
| Snell,I. | 4.07 | 3.76 | (0.31) | |
| Meche,G. | 3.97 | 3.67 | (0.31) | |
The importance of this indicator can not be under estimated
and typically over the stretch of a season there is reversion to the mean
for a great majority of the players that are outliers. Fantistics
Subscribers can find the XERA indicator built into our
2008 pitcher
projection ERAs, and can also view the outliers during the season within our Player
Charts database.
In a few days we'll highlight the guys who
had an ERA which was higher than expected in 2007 (and probably will be
undervalued in most 2008 draft rooms).
Have a great day!
-Anthony A. Perri
