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Tuesday, January 19, 2010

Developing Player Value: Defensive Value per 20 Minutes (DV/20)

NOTE: After having this up for a couple of days, I decided to make a serious revision to this post.  Take a gander, and Andy Sutton...I pardon you.

So, when you think of a good defenseman, what names come to mind?  Scott Stevens, Nicklas Lidstrom, Bobby Orr, Ray Bourque, Paul Coffey, Garth Butcher...

Gaaahhh!  Okay, so most of those guys are actually great defensemen, but it raises an important point about who we consider a talented defenseman: they are often great at particular nuances of the position, so much so that it tends to make us ignore other aspects.  Typically, those "other aspects" (with the exception of Stevens) involve the ability to make defensive plays such as takeaways and checking.

This post is the first in a series I'm devoting to forming a performance value for defensemen.  Initially taking the NHL statistics from the 2008-09 season, I want to find a metric that will celebrate both the offensive and defensive types of blueliners.  We'll go over these metrics one at a time, eventually putting them together for a complete player value.

Defensive Value per 20 Minutes, or DV/20, takes a select amount of defensive plays, in particular hitting (which intends to disrupt or intimidate offense) and takeaways (which interrupts offense), and off-sets it with the defenseman's ability to avoid minor penalties in doing so.  After some deliberation, I decided that I should add blocked shots as well.  Initially, I was going to give that its own category, but when I bring the values together I would find myself granting similar values to blocking shots and a holistic defense metric, which seemed wrong.

Hits and takeaways are actually very controversial stats; hits are counted differently at each rink, as are takeaways, leaving a substantial amount of variance.  Scorekeeper's hitting bias, as noted by Behind the Net's Gabriel Desjardins, can typically be helped (albeit imperfectly) by taking the count of hits during away games. I extrapolated that suggestion to finding the per game average, and multiplying it back out to the games played by the hitter.  Cal Clutterbuck, for instance, loses about 45 hits when you do this, which gives you an idea of how different they were counting it in Minnesota.  Takeaway bias is harder, because the statistics aren't kept well enough to determine home and away takeaways (or at least I haven't found one that shows all the players that played last year).  So I'll leave that one, hope the home biases cancel out over the season, and wait until I can find (or be directed to) something better.

I handled blocked shots similarly, taking away game blocked shot totals, finding the per game, and fitting it to the actual games played of the players.

But simple volume of these actions is not enough.  Being able to hit people or take away the puck takes a certain amount of skill to get the achieved effect without hurting your team.  Therefore, I determined hits and takeaways per 20 minutes of play (roughly, the average playing time for a regularly-used defenseman), and subtracted the penalty minutes per game a player accrued due to doing those actions illegally.  For hits, they were subtracted for roughing, elbowing, cross-checking, interference, and boarding minors; for takeaways, they were docked for tripping, hooking, holding, slashing, and high-sticking minors.  Also for the hits, I included any non-fighting majors, assuming that they would involve physical play.

Finally, I was certain that I wanted to include an earlier metric, PPM/15 (in this case, PPM/20), to adjust for players who not only played solid, clean hockey but could also gain a few powerplay opportunities for their team.  The inclusion of this metric is debatable, but I have yet to find someone to convince me that non-coincidental minors can truly help your team.

I set the minimum games played at 20 to get out the rooks, goons, gimps, and anomalies.

The league average over 234 defensemen was 2.47 DV/20.  Your NHL leaders and losers (with Games Played and Average Time On Ice):

NHL Top 5, 2008-09
1. Erik Reitz, Rangers/Burkes/Adjectives, 5.50 --- 42 GP, 9:57 ATOI
2. Garnet Exelby, Hotlanta,  4.80 --- 59 GP, 16:43 ATOI
3. Denis Gauthier, Queens, 4.75 --- 65 GP, 14:32 ATOI
4. Tyler Sloan, The Bandwagon, 4.74 --- 26 GP, 16:38 ATOI
5. Anton Volchenkov, Senate, 4.60 --- 68 GP, 20:08 ATOI

NHL Bottom 5
230. Rob Blake, Jaws, .92 --- 73 GP, 21:16 ATOI
231. Sheldon Souray, Jiffy Lubes, .91 --- 81 GP, 24:50 ATOI
232. Marc-Andre Bergeron, Adjectives, .90 --- 72 GP, 16:54 ATOI
233. Cory Murphy, Shockers/Garfields, .80 --- 32 GP, 17:57 ATOI
234. Brett Lebda, Detroit Rock City, -.07 --- 65 GP, 13:38 ATOI

As you can see, some serious surprises here.  Erik Reitz, interestingly enough, is terrorizing the KHL right now, and getting called for a few more minutes than he did here (NHL: 1.5 PIM/G, KHL: 4.2 PIM/G).  Nevertheless, his 42 games last year were an impressive display of hitting and takeaways with minimal adverse damage to his teams.

Think defense is unappreciated?  Take a look at those games played and ice times.  And I guarantee you those guys on the top were not all injured.

I thought that this metric would overwhelmingly support big hitters, so I was interested to see Rob Blake and Sheldon Souray so low.  Looking back at the numbers, though, showed that they were simply terrible at taking minor penalties.  In general, though, hitters and strong shot-blockers were favored, and that is part of the reason I wanted this to be only one part of the entire defenseman value metric.  And Brett Lebda is decidedly unfavored.  Wow.

Mad props, by the way, to Tyler Sloan for performing well in his rookie season.  It's all the more impressive that his first year came after seven years of slogging through the minors.  As of this writing, he's still getting little play for a team that could use sound D.

In the next installment, I'll throw Shot Value per 20 Minutes at you.  And remember, always look out for...oh no...aaarrrrrggghhhh...

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