Sunday, September 23, 2012

NFL Team Rankings - Week 3

As promised yesterday, here are the NFL Team Rankings as of Week 3 (with lines updated as of Sunday morning).  For those of you new to this site, these rankings are an attempt to reverse engineer an implied power ranking from the Vegas point spreads.  If you're gambling on the NFL, think of this as competitive intelligence, in that your competition is Vegas, the sportsbooks, and the combined wisdom of the betting public.  The goal of this site is to provide greater clarity on what may be driving how point spreads (and over/unders) for each game are being set.

My Methodology page has a simple example of what I am doing below.  You can also refer to my posts (here and here) at Advanced NFL Stats Community for more detail.

The Rankings

Here are the rankings, with lines updated as of the morning of September 23 (data courtesy of Killer Sports).  First, a glossary of terms:

  • LstWk - The team's ranking as of a week ago.  Things will be volatile in the early weeks of the season.
  • GPF - Stands for Generic Points Favored.  It's what you would expect a team to be favored by against a league average opponent at a neutral site (if the team is at home, just add 2.5 points)
  • oGPF - Stands for Offensive Generic Points Favored.  It's the component of a team's GPF that is attributable to offense.  I can derive this by combining the information in the point spread and over/unders.  My post at Advanced NFL Stats Community has more detail.
  • dGPF - Stands for Defensive Generic Points Favored.   It's the component of a team's GPF that is attributable to defense.

The Packers sit atop the rankings once again, which shouldn't be too much of a surprise.

Offense or Defense?

The standard deviation of oGPF is 2.7 points and the standard deviation of dGPF is 1.7 points.  This means that there is more variation in team strength due to offense rather than defense.  You could interpret this as saying that defenses are somewhat at the mercy of what an offense can or can't do.

Another number of note is the correlation between oGPF and dGPF.  They are positively correlated (correlation coefficient of 0.38).  In football, a good offense can help out its defense and vice versa.  Teams that score a lot move the ball down the field, so even if the drive stalls, they put the opposing team in unfavorable field position.  So, the oGPF and dGPF rankings are probably not "pure" rankings of team defense and offense, but a linear combination of the two.

2 comments:

  1. Are these rankings updated weekly? If not, when might week 4 be updated? Thanks.

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  2. I'm planning on a post tomorrow morning, and then daily updates after that (similar to my MLB rankings). In the short term, here are the rankings as of today (Friday):

    team GPF
    NE 6.2
    GB 5.9
    SF 5.7
    TEX 5.6
    BAL 4.4
    PIT 3.4
    ATL 3.2
    NYG 2.6
    PHI 2.5
    DAL 2.3
    NO 1.8
    DEN 1.6
    CHI 0.9
    SD 0.9
    DET -0.2
    BUF -0.4
    NYJ -0.7
    CAR -0.7
    SEA -0.8
    CIN -1.3
    MIN -1.6
    KC -1.7
    ARZ -2.1
    RAI -2.3
    TB -2.5
    WAS -2.5
    TEN -3.9
    IND -4.6
    JAC -5
    MIA -5.2
    CLE -5.5
    STL -6.3

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