DIGR: Defense Independent Goalie Rating

by PhilliePhan24 on Oct 17, 2011 6:57 PM EDT

I saw a thread about this on another website and I find it pretty intriguing.

I know there are quite a few posters around here who are really into hockey sabermetrics (or 'advanced' statistics in general), so I would like to hear your thoughts on this.

Basically, it is a statistic that adjusts save percentage to show the true ability of the goalie, without his defensemen.

Now I'm not too verse in advanced hockey statistics, but I'm guessing this is similar to baseball statistics which take out fielding to show the true ability of the pitcher.

Here is the link to the professor's slideshow about the topic

http://www.slideshare.net/sloansportsconf/digr-a-defense-independent-rating-of-nhl-goaltenders-using-spatially-smoothed-save-percentage-maps

Also, here’s the full list of goalies and their DIGR (min. 1,000 shots faced last season):

1. Tim Thomas (.931)
2. Roberto Luongo (.927)
3. Jonas Hiller (.927)
4. Ilya Bryzgalov (.923)
5. Cam Ward (.923)
6. Marc-Andre Fleury (.923)
7. Devan Dubnyk (.922)
8. Corey Crawford (.922)
9. Carey Price (.922)
10. Pekka Rinne (.920)
11. Henrik Lundqvist (.918)
12. Jaroslav Halak (.918)
13. Tomas Vokoun (.918)
14. Ondrej Pavelec (.918)
15. Sergei Bobrovsky (.917)
16. Michal Neuvirth (.916)
17. Ryan Miller (.916)
18. James Reimer (.914)
19. Antti Niemi (.914)
20. Dwayne Roloson (.914)
21. Kari Lehtonen (.913)
22. Craig Anderson (.912)
23. Niklas Backstrom (.912)
24. Jonathan Quick (.909)
25. Martin Brodeur (.909)
26. Jimmy Howard (.907)
27. Steve Mason (.906)
28. Dan Ellis (.904)
29. Miikka Kiprusoff (.902)
30. Peter Budaj (.902)
31. Brian Elliott (.900)
32. Nikolai Khabibulin (.900)

Note: This is my first fanpost so bear with me if I have any mistakes.

This item was written by a member of this community and is not necessarily endorsed by Broad Street Hockey.

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Comments

I was discussing the potential of something like this on one of the game threads (think it was after Game 2). Glad someone’s put their effort into it. Fascinating stuff.

Simon Gagne AND Mike Richards may move between towns, wear new jerseys and call different arenas home but, at the end of the day, they will both always be Philadelphia Flyers.

One day Sean Couturier will win the Conn Smythe. You heard it here first.

by PursuitOfLappyness on Oct 17, 2011 9:50 PM EDT reply actions

Just flipped through the slide show, think my brain might be melting now. So basically this is a new type of save %, normalized for all goalies since it’s figured with shot location, and type of shot (don’t call it quality?)?

G, the second coming of Foppa.
Embrace the Jagr.*

by JerseyDriver on Oct 18, 2011 12:35 AM EDT reply actions

Right. So if a goalie faced an unusually number of high wrist shots from six feet in front of him and low number of slap shots from the point, that will be normalized out.

My take on it (as I commented on the Fly-By today: I love the idea in a first-principles kind of way, but I’m a little disappointed that I haven’t seen any tests of whether this is empirically a better way to measure goalies.

Is DIGR more persistent than Sv%? Is it better at predicting future performance with a limited sample size? Is the difference between Sv% and DIGR (which is presumably the defense’s contribution) persistent and/or predictive? When a team switches goalies, can you predict the new Sv% from the team’s previous defense and the goalie’s previous DIGR?

A couple of right answers to these questions and I would become a missionary for DIGR. Without those answers, it’s something I’m interested in but probably won’t use much. My intuition tells me it ought to be better, but the stats about goaltending are primitive enough that I’m not ready to trust intuition yet.

@BSH_EricT
Writer at Broad Street Hockey

by Eric T. on Oct 18, 2011 3:27 PM EDT up reply actions

Good to know, thanks for the reply.

G, the second coming of Foppa.
Embrace the Jagr.*

by JerseyDriver on Oct 18, 2011 6:19 PM EDT up reply actions

(repost from fly-by)

I finally got moved to download and check the persistence from ’09-10 to ’10-11.

For the 33 guys who had a DIGR published for both seasons, the correlation between their ’09-10 and ’10-11 DIGR was 0.29. The correlation between their ’09-10 and ’10-11 Sv% was .30.

I remain unconvinced that the complications are adding enough value to be worth switching away from the easily understood, easily found metric.

@BSH_EricT
Writer at Broad Street Hockey

by Eric T. on Oct 18, 2011 7:06 PM EDT up reply actions

I know it would be a tiny sample, but can you compare the change in save % vs. DIGR for goalies who changed teams over the offseason? If the DIGR was more stable than the save% that would make somewhat intuitive sense right? But I’m interested to find out if that’s true.

Simon Gagne AND Mike Richards may move between towns, wear new jerseys and call different arenas home but, at the end of the day, they will both always be Philadelphia Flyers.

One day Sean Couturier will win the Conn Smythe. You heard it here first.

by PursuitOfLappyness on Oct 21, 2011 8:01 AM EDT up reply actions