Defensive Contribution and QualComp/QualTeam

I think it makes sense to incorporate QualComp and QualTeam into DGVA.  It just doesn't make much difference.

I had been pondering whether it helped to utilize QualComp and QualTeam in computing DGVA from GAON and GAOFF. If I understand QualComp correctly, it is the average of (GFON/60 -GFOFF/60) – (GAON/60 – GAOFF/60) for all opponents faced. As such, it is in the same units as DGVA/60, and I think it makes sense to adjust GVA/60 accordingly. Presumably, I could scale DGVA/60 by multiplying by (1 + QC). It seems easier to add QC to DGVA/60. However, since QC is both offense and defense, and DGVA is just defense, I think adding 0.5*QC makes the most sense. Later, if/when I look at OGVA, I would add the other half.

QualTeam to me is a little less clear, since a player’s performance influences the GAON/60 rates of his teammates. I’ll think about whether there is a easy way to pull out the portion of QT independent of the player we are looking at. In the interim, from a symmetry standpoint if nothing else, we can subtract (to keep the signs and magnitudes correct) 0.5*QT from DGVA/60.

Looking at defensemen who had 20+ games last season, QC runs from +0.150 to -0.184. QT runs from +0.380 to -0..317. The ranges are greater than I would have guessed.

I reran the calculations using adjusted DGVA/60, and there really is not much change. The top 20 are basically the same. I listed them in Appendix A. Jack Johnson remain by far the worst, at -38.95 In looking at the differences between raw GVA and adjusted GVA, only 9 of 304 defensemen saw more than 2 goals difference. I listed the top 5 and bottom 5 in Appendix B. Zbynek Michalek goes up 3.95 due to QualTeam of -0.30. Conversely, Nicklas Lidstrom goes down 3.81 due to a QualTeam of +0.38

Appendix A

Top 20 Defensemen in Adjusted GVA

Appendix B

Biggest differences between Raw GVA and Adjusted GVA