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Calgary Flames Adjusted 2013 Possession Rates
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Kent Wilson
Apr 30, 2013, 10:55 EDTUpdated: Apr 29, 2013, 22:18 EDT
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pic via Shane Henderson
Another year is over and we’re left to pick through the rubble a bit. The first order of business is evaluating the various skaters by possession – or the ability to drive play, which is one of the metrics in hockey that has a strong signal-to-noise ratio.
That said, we can correct corsi for a number of factors be better put it into context and up the level of confidence with which we can say the number is indicative of the player’s ability and not some other factor (be it luck or circumstances). Two major issues with raw possession rate is zone start (or how often a player starts his shifts in the offensive zone) and quality linemates and opposition (playing with or against good/bad players).  
Good news is, Oiler fan and mathy blogger Michael Parkatti came up with a regression equation that helps correct for both issues recently.
The formula would then be:
Expected raw Corsi = -11.91 + QualDiff * 1.00 + Off ZS% * 0.24
So, a player with QualDiff of 0, and a zone start rate of 50% would have an expected Raw Corsi of:
Expected raw Corsi = -11.91 + 0 * 1.00 + 50 * 0.24 = -0.15
…
The formula suggests that Corsi will increase by 1 for every unit increase in his quality of teammates and every unit decrease in his quality of competition. His Corsi will increase by one about every 4 more percentage points in his zone start. A player with a zero QualDiff and starting every faceoff in the defensive end is expected to have a -11.91 Corsi, reflected in the intercept above.
So that’s a lot of numbers and formulas and such, but what it gives us is a really easy way to plug in raw corsi rates and adjust for a players circumstances. That means it’s easier to compare guys on the same club across various lines and roles.
To the tables!

The Forwards 

PlayerCorsi QoCCorsi QotQualdifZS %corsi expectedcorsi oncorsi adjusted
Backlund
0.52
-4.98
-5.50
45.40
-6.52
2.14
8.66
Stempniak
1.20
-4.39
-5.59
43.50
-7.06
-0.55
6.51
Stajan
1.26
-4.29
-5.55
42.00
-7.38
-3.13
4.25
Glencross
0.50
-3.85
-4.35
49.30
-4.43
-1.17
3.26
Cammalleri
-0.01
-4.79
-4.78
45.40
-5.80
-3.17
2.63
Begin
-1.84
-6.49
-4.65
46.30
-5.45
-4.01
1.44
Jackman
-1.81
-6.61
-4.80
46.90
-5.45
-4.38
1.07
Hudler
0.03
-4.69
-4.72
44.10
-6.04
-5.32
0.72
Tanguay
0.95
-3.73
-4.68
45.20
-5.74
-5.12
0.62
Horak
0.52
-6.32
-6.84
39.20
-9.35
-9.65
-0.30
Cervenka
-0.68
-4.85
-4.17
43.80
-5.56
-6.05
-0.49
Jones
-0.89
-6.81
-5.92
45.80
-6.83
-8.78
-1.95
Baertschi
-0.93
-4.78
-3.85
48.20
-4.19
-6.99
-2.80
Reinhart
-0.28
-5.31
-5.03
40.00
-7.34
-14.39
-7.05
McGrattan
-2.56
-6.90
-4.33
57.10
-2.54
-19.74
-17.20
The first three columns have to do with each forwards’ quality of competition and linemates, as well as the "difference" between them (Qualdif). Next, we have each guys zone start ratio (offensive zone/defensive zone) and his resultant expected corsi based on Parkatti’s equation.
Corsi on is each skaters’ actual corsi/60 rate (via behindthenet.ca) and adjusted corsi if the difference between his actual and expected rate – meaning a number above zero indicates a guy outperformed his expected rate according to his circumstance (that’s good!) while a negative number means he underperformed (that’s bad).
The table is sorted by adjusted corsi.
Of course, none of the results should surprise anyone, but they are interesting nonetheless. The guys who looked good by eye and by underlying numbers come out well here: Backlund, Stempniak, Stajan and Glencross lead the way. Jackman and Begin come out well for minimum wage fourth liners too.
Roman Horak actually moves way up with this method thanks to rough circumstances, but doesn’t quite come out even. Still, not a terrible result for a kid. Baertschi isn’t quite there, but his improvement was rapid upon his recall and remember we’re talking about pretty small numbers here.
Reinhart, on the other hand, is further behind, especially because he doesn’t bring the same offense or PP prowess as  Sven.
Finally, Brian McGrattan is obviously an enforcer, with typical enforcer type numbers.

The Defense

Next up, the blueline:
PlayerCorsi QoCCorsi QotQualdifZS %corsi expectedcorsi oncorsi adjusted
Brodie
-0.42
-4.87
-4.45
47.90
-4.87
0.97
5.84
Wideman
0.50
-4.56
-5.06
45.50
-6.05
-2.98
3.07
Sarich
-1.97
-5.83
-3.86
41.20
-5.88
-3.28
2.60
Giordano
1.30
-4.36
-5.66
41.00
-7.73
-5.96
1.77
Smith
-0.68
-5.31
-4.64
53.30
-3.75
-4.62
-0.87
Carson
-1.40
-7.04
-5.64
63.60
-2.28
-6.21
-3.93
Butler
-0.12
-5.20
-5.08
46.60
-5.81
-13.50
-7.70
Again, no big surprises, except for maybe Cory Sarich who despite his various limitations never has terrible underlying numbers. Brodie and Wideman lead the way with the kid out in front. Giordano also is somewhat vindicated by this process thanks to the high difficulty of his role this year.
On the other hand, Carson and especially Butler don’t really look like NHLers. Butler is out on an island of suck all by himself, in fact. That might have been understandable with the dude trying to play over his head last season, but this year he was mostly a third pairing guy and still couldn’t even come close to breaking even.

Conclusion

The best news for the Flames org is their two main youngsters are already the best possession players on the team and the Flames have the option to sign them both up for cheap this summer. Niether Backlund nor Brodie is a superstar in the making, but they’re both already better than your average NHLer, are young enough that they should improve, and will not cost an arm or leg to re-sign.
Caveat emptor; we’re talking about a small sample of games here in general thanks to the shortened season, and even smaller in individual cases thanks to injury and other factors (like playing between the AHL and NHL for the kids). In addition, with the team trying to lose down the stretch by throwing every non-NHL body they could on the ice (and Hartley not matching lines or anything), some of this sample isn’t exactly representative. So keep thosee factors in mind. 

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