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Flames Adjusted Zone Shift - UPDATED

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JLikens of the always interesting Objective NHL blog has been working on a few things this off-season, one of which is adjusted zone shift. We've discussed this metric in the comments now and then, but here's a full explanation for those unfamiliar:

One thing I wanted to look at was changes in zone, the guys who are getting the puck going in the right direction. And since the NHL doesn't publish their zone time information any more, I just went by faceoffs. If a shift started in the defensive zone the the player gets a plus, and a minus for starting in the other end of the rink. Also if your shift ends in the offensive zone you get a plus, and you get a minus if your shift ends at the bad end of the ice.

This is the method for determining a players raw zone shift. JLikens looked at the stat and decided an adjustment was in order:

It appears that starting a high proportion of your EV faceoffs in your own zone relative to your team average - in other words, having a high PLAYER ZONE DIFFERENTIAL - is pretty favorable toward ZONE SHIFT.

...

Long story short: It's easier to have a good Zone Shift number if you're starting more in your own end of the rink relative to your teammates, and if the metric is to be worth anything at all, this ought to be corrected for.

And I've attempted to do exactly that. Contained below is a listing of the league's best and worst players in ADJUSTED ZONE SHIFT - adjusted because the stat attempts to control for the above bias.

Meaning the results were being skewed towards defensive forwards and defensemen. He has a full explanation of his adjustment methodology at the linked article, but, in short, J subtracted the players starting and ending zone ratios from the teams starting and ending ratios. There's probably more to be done on this issue, but this is a good first step in my estimation as the top and bottom players in the league by adjusted ZS seem to pass the initial sniff test.

Anyways, J was good enough to send me the adjusted ZS numbers for the entire Flames club, as follows:

The results are fairly surprising. Aucoin, Moss, Glencross, Langkow and Giordano come out looking pretty good, while guys like Boyd, Bourque, Iginla and Phaneuf apparently struggled. Boyd is to be somewhat expected, but that so many good players were so far in the red makes me scratch my head. The entire club seemed good at moving the puck forward last year, but one wonders if the Glencross/Moss/Conroy line was driving the bus in this regard even more than was suggested previously. 

JLikens will no doubt be adding to this body of work as the summer matures, so expect a follow-up in the near future.

UPDATE -

JL recently sent me this reponse to the issues raised in the comments:

The numbers are different for two reasons.

1.  The numbers at Vic's site don't include shifts that ended in goals at EV, and my original numbers didn't take that into account.  However, the data that I've sent you includes shifts that ended in goals.
 
2. The correction formula is slightly different now due to changes made to the data (namely, the correction described in 1).
 
Also, it should be emphasized that each player's adjusted zone shift (and this applies to unadjusted zone shift, too) is a team relative stat.  Accordingly, it's somewhat biased against players on strong teams (zoneshift, wise).  The Flames players with poor (adjusted) zone shift numbers have only done poorly relative to their teammates.  I suspect that most of Calgary's players are pretty effective at moving the puck in the right direction in absolute terms.

Hopefully this clears things up a tad.