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# Oilers' Zone Differential

A couple weeks ago I presented the concept of Expected ZoneFinish, setting the stage for a sequel with this closing paragraph:

Of course if I wanted to be truly scientific about all this, I would repeat the above study with the forwards, or for other seasons, but for now, I've seen enough to accept 0.3 as my working fudge factor from which we can derive Expected ZoneFinish. On an individual level, it's pretty darn interesting to compare that number to Actual (adjusted) ZoneFinish. But that's a subject for another day.

It now is another day, so why not explore that idea in a little more depth? We have seen how a large group of players (200 defencemen with 41+ GP) performs, proving Gabe Desjardins' supposition that "hockey swings hard to the equilibrium"; what can we learn about individual players? While this idea has potential on the macro level, I prefer to start with a micro-study of the players I know best, namely, the Oilers.

First, though, I should mention that I did repeat the study with the forwards, at least the 380 of them who played 41+ GP. There are interesting differences from the defencemen, especially on the Quality of Competition side of things which is much more randomly distributed among the forwards. But one thing that held true was that forwards generally finished their shifts a lot closer to centre-ice than they started them, with the ZoneFinish stats having only about 30% the range as ZoneStarts.

So I calculated Expected ZoneFinish numbers for the Oilers (10+ GP) based on this "working fudge factor", and compared that to where they really did force their faceoffs. First up, the forwards:

 NAME OZS% ExpOZF% ActOZF% ZoneDiff ALES HEMSKY 43.5 48.1 53.5 +5.4 DUSTIN PENNER 45.6 48.7 50.7 +2.0 GILBERT BRULE 48.4 49.5 51.1 +1.6 RYAN STONE 52.7 50.8 52.3 +1.5 MIKE COMRIE 47.6 49.3 49.9 +0.6 PATRICK O'SULLIVAN 49.9 50.0 50.5 +0.5 RYAN POTULNY 47.1 49.1 49.1 0.0 RYAN JONES 47.6 49.3 49.1 -0.1 ANDREW COGLIANO 49.1 49.7 49.5 -0.2 SAM GAGNER 48.8 49.6 49.4 -0.3 MARC POULIOT 51 50.3 49.8 -0.5 ROBERT NILSSON 48 49.4 48.9 -0.5 J-FJACQUES 51.5 50.5 48.6 -1.8 ZACK STORTINI 46.6 49.0 46.8 -2.1 FERNANDO PISANI 46.4 48.9 45.4 -3.5 SHAWN HORCOFF 45.3 48.6 44.8 -3.8 ETHAN MOREAU 45.3 48.6 43.0 -5.6

Reading across the top line of that, Ales Hemsky started 43.5% of his end zone faceoffs (neutral zone draws omitted) in the offensive zone (OZS%), meaning he took about four draws in his own zone for every three he got in the attacking end of the ice, a tough assignment. Nonetheless, given the normal 70% flow to the equilibrium, Hemsky could be expected to finish about 48.1% of his shifts in the offensive zone (ExpOZF%). Actual ZoneFinish (ActOZF%) - including an adjustment for goals scored while Hemsky was on the ice, which as I understand it, are nominally scored as neutral zone faceoffs - indicates the play finished at the good end of the ice some 53.5% of the time that Ales was out there. The last column, ZoneDifferential, is simply the +/- between where the play really ended up compared to expected rates. In Hemsky's case, that differential is a whopping +5.4%, a very impressive number more than twice as good as any other Oiler and, I would daresay, among the league's elite. When Ales Hemsky is on the ice, the puck is going in the right direction more often than not.

Dustin Penner is a solid second on the club, well behind Hemsky, but Dustin also had to play all 82 games, the last 60 of them with no Hemmer to be seen. Any stat that suggests that Ales Hemsky and Dustin Penner are the top two forwards on the club is a stat that has passed at least one test. Encouraging to see Gilbert Brule next in line; some of that was riding Penner's coattails no doubt, but Dustin himself seemed to do better when he had Brule on his starboard side. For sure the pair showed some synergy on a squad that had precious little of it.

The other three guys on the positive side of this particular ledger are now ex-Oilers, led by Ryan Stone, who had the best underlying numbers of any zero-goal scorer I've ever seen. Here's another one. While Stone's bad knee largely ruined his season, he showed enough in limited playing time to have me concerned that the Oil may have blown it in letting him get away (to Calgary of all stinkin' places). The prospect of Stone becoming GlenX 2.0 is more than a little concerning.

On the bottom end of the list, why there's good old thecaptainethanmoreau. What a surprise. What another vote of confidence for the method.

Actually, I'm tempted to give the three vets on the bottom of the pile something of a break, as they collectively faced by far the toughest QualComp of the forward corps. Still, Shawn Horcoff did exceptionally well by the ZoneDifferential metric in 2008-09 even with tough comp, yet stumbled badly in '09-10, which pretty much matches what my eye saw of Horc this past campaign.

Turning now to the defence:

 NAME OZS% ExpOZF% AdjOZF% ZoneDiff LADISLAV SMID 46.8 49.0 51.4 +2.4 TOM GILBERT 49.6 49.9 51.6 +1.7 STEVE STAIOS 50.7 50.2 50.5 +0.3 RYAN WHITNEY 48.8 49.6 49.6 -0.1 DENIS GREBESHKOV 47.9 49.4 48.9 -0.5 LUBOMIR VISNOVSKY 50.2 50.1 49.6 -0.5 SHELDON SOURAY 52.6 50.8 50.2 -0.6 JASON STRUDWICK 46 48.8 47.4 -1.4 AARON JOHNSON 45.9 48.8 46.7 -2.1 THEO PECKHAM 38.9 46.7 44.4 -2.2 TAYLOR CHORNEY 39.2 46.8 41.3 -5.5 DEAN ARSENE 48.8 49.6 34.6 -15.1

While the forward corps was largely static in '09-10 (Steve Tambellini was busy evaluating), the same can't be said of the defence, which saw major turnover. I have highlighted in blue those players who ended the season as Oilers after starting out elsewhere, and in copper those guys who played the bulk of the year with the Oil before moving on at the deadline. Behind the Net stats don't differentiate for players with multiple teams so I simply have showed full-year totals. I'm pleasantly surprised to see Ladislav Smid atop the list, and not surprised at all to see Tom Gilbert hot on his heels. Both guys saw their percentages pass through 50% in the positive direction, which is clearly a good showing with or without any whizzy adjustments and expectations. Most of Smid's positive results have been credited to his erstwhile partner Lubomir Visnovsky, so it's a little shocking to see Lubo passing through the 50% barrier in the opposite direction. Mind you those numbers are so close to 50% each way that I would categorize him as a neutral player by this metric, but frankly, I expected him to be a pretty strong positive and that wasn't the case in 2009-10.

Near the bottom of the list we see some expected names in Strudwick, Peckham, and Chorney. By the old ZoneShift metric Chorney actually looked to be a positive driver of play, but that's where Expected ZoneFinish reveals the truth that he was in over his head. Those words don't even begin to describe the atrocious results of Dean Arsene. Small sample size and all that, but I think this stat shows pretty conclusively that the play went backwards when he was on the ice. Three times as bad as Taylor Chorney is r-e-a-l bad.

Anyway, all this is still in the exploratory stage, and I welcome any comments and suggestions as to how to improve the method or the interpretation of the results.