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
would be prime candidates not to achieve the same success
in ERA in 2007 as they had the previous year. I was right in all 4
situations as all 4 saw a rise in their ERA the following season (although
Verlander went on to have a better season than the prior year). In 2005,
I predicted that
Jorge
Sosa, Zack Duke, Carlos Silva, and Kevin Millwood
would be prime candidates not to achieve the same success in ERA in 2006
as they had the previous year and I humbly was correct in all 4 instances
again.
The reason I dropped the names above is not to brag or
boast, but rather to show the efficiency of this indicator.
Of course, 8 correct observations makes for much less
than a scientific study, however XERA is a statistic that I have
backtested using data since 1992, and the results are overwhelming.
Pitchers who had a lower ERA than expected in an observed year by more
than 50 points and also had an ERA that year which was 50 points less than
their 3 year average, posted a 50 point or more rise in ERA the following
season. This held true in 77% of the individual cases!
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).
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