Greg Robinson

[ed: bump.]

I hope this kind of analysis hasn't been done already; if so, my apologies. I was wondering, in light of Brian's analysis of the defense, if we could quantify the effect of having Mattison rather than GERG as our defensive coordinator. To that end, I have tried to quantify the effect of having Greg Robinson as defensive coordinator: the GERG effect. I looked up the scoring defense ranks of Michigan, Syracuse, and Texas for 2003-2010 (data from Rivals). They are as follows:

	2003	2004	2005	2006	2007	2008	2009	2010
Texas	33	14	5	26	45	18	12	49
Syracuse	61	71	70	54	104	102	81	17
Michigan	7	38	22	16	23	84	76	107
GERG		14	70	54	104	102	76	107

GERG was DC at Texas in 2004, HC at Syracuse in 2005-2008, and DC at Michigan in 2009-2010. We can therefore display the data graphically as follows (note that the Y axis is team defense scoring rank): We can also try to calculate a crude GERG effect by comparing the average rank of these defenses with and without GERG. This yields the following:

	non-GERG	GERG	difference
Texas	25.3	14	-11
Syracuse	57.5	82.5	25
Michigan	31.7	91.5	59.8

Note that positive is bad and negative is good. So GERG's Texas defense was 11 ranks better than the non-GERG average, whereas his Michigan defenses were 60 ranks worse than the non-GERG average.

To calculate the overall GERG effect, we simply multiple the differences in rank by the number of years at each school, divided by the total number of years (7), to arrive at our overall GERG effect of 29.77 [this figure has been updated]. That is, on average, GERG adversely affects the scoring rank of the defenses he is associated with by 30 positions.

If we take Brian's projection of Michigan's 2011 defense (82nd), and subtract 30 ranks to adjust for the GERG effect, we get to 52, a ranking that a number of commentators were predicting based on their "gut" feeling of player development and the new coaching staff's abilities (particularly Mattison).

Again, this is wild speculation, and incredibly simple -- hopefully it is not completely misguided. Other more advanced metrics should also be used. I am aware that there are far more variables at work that determine how good a defense is--and it is almost certain that GERG was not allowed to run his defense at Michigan. Also, it is likely that Mattison is an excellent DC, something that this analysis does not account for. I was still curious to see if anything could be done to account for the coaching change.

UPDATE: I made an arithmetical error which has been corrected. Also, I ran the same analysis with S&P+ play-by-play ratings from Football outsiders and got a GERG effect of 27.75 ranks (using only Syracuse and Michigan; S&P+ data are only available from 2005 and later).

[ed: We should be taking all of this, including my original post, with a grain of salt because of sample size issues.

That said, Michigan was an the extreme outlier because of its youth and trying to run two different schemes, one of which was something no one's ever tried before, and could expect to rebound further with Mattison--and more importantly, sanity--hanging around campus. The numbers offered here in the two posts (54 using S&P+ data and 82) seem like the ends of a range of reasonable expectations.

The moral of the story is the same one learned by the offenses of Notre Dame in 2008 and Michgian in 2009--you're going to be a lot better but still very far from good.]