Calder Trophy Race Analysis: dCorsi and Usage Comparison

Recently I contributed a piece to Hockey Prospectus where I took a look at the Calder Trophy race from an analytical standpoint and tried to point out who is standing out using advanced stats rather than traditional stats. Do me a solid and take a look at the article here:

http://www.hockeyprospectus.com/a-statistical-analysis-of-the-calder-trophy-race/

In short, I came to the conclusion that Filip Forsberg is the front-runner for the Calder thus far, but the strong rookie d-men, Aaron Ekblad and John Klingberg, are making cases for themselves as well. One thing I didn’t really get to do in that piece is look at all of the candidates usage numbers and how they are producing compared to what they are expected to do. A lot of the time, if not all the time, the Calder goes to the rookie who gets the most points or is the most productive to their team. However, rookies rarely play a large role with big minutes unless you are a top-5 pick or have developed through junior and multiple years in the AHL. For this reason, I want to look at the rookies of 2014-2015 and their dCorsi numbers. For those of you that aren’t aware of what dCorsi is, you can read a basic introduction to it here and you can also take a look at a more mathematical description of the methods and procedures in its development and deployment here.

I like what Steve Burtch (@StephenBurtch) has done with this method. It allows for us to look at not only how players are being deployed (looking at their Expected Corsi numbers), but it allows us to compare players using their delta numbers, which are the differences between their expected and observed corsi for and against numbers. What it lets us do is compare players across different usages in order to see which players are actually under- or over-performing. A high dCorsi shows that a player is contributed more to the possession game than he is expected, and vice-versa for a low (negative) dCorsi number. The dCorsiImpact number simply shows the cumulative sum of “dCorsi” a player contributes, based on their total ice time for the season. Now, on to the comparison.

The players I am looking at were determined in my HP piece, and if you are wondering why I selected the players I did I would suggest you read that piece to gain that understanding. The dCorsi numbers are available on war-on-ice.com, under the “Labs” tab, and it allows you to look at all players or a player across their career (since 2005-2006). First, lets take a look at the dCorsi60 the 8 rookies in my analysis:

dcorsi60
Rookie dCorsi per 60 minutes in 2014-2015. Numbers extracted from war-on-ice.com on February 17, 2015.

Looking at this, my previous Calder prediction may be a bit off. Forsberg is not doing so well in terms of his dCorsi numbers, as he is posting a corsi number that is 0.65 below what he is expected to produce. This may partially be a result of his tough minutes and increased ice time compared to the other rookies.

Anders Lee and Mark Stone are what stand out here. Lee has been fairly good production wise this season, finding his way onto a line with superstar John Tavares. Stone is making a big impact as well on the Senators, but I did not expect the usage numbers to be as high as they are here.

Ekblad is putting up a fairly low number in the dCorsi category, but this is probably because he is assuming top pairing minutes on the Panthers this year.Klingberg, who has outstanding over the past month or so, is living up to his big time minutes and is pulling ahead of Ekblad in this comparison. These are both highly talented defensemen who will be valuable pieces in the upcoming years.

The dCorsi number is only one way that Burtch has allowed us to view the usage of individual players. The dCorsiImpact number is very helpful when trying to quantify the possession impact of a player over an entire season or over a span of games. Here is a visual of the 8 rookies and their dCorsiImpact (which follows mainly the same pattern as the dCorsi60 number because it is that number multiplied by the number of 60 minute time periods they have played):

dcorsiimpact
Total dCorsiImpact for the 8 rookies in my analysis. All data extracted from war-on-ice.com on February 17, 2015.

The smart and clever guys at WarOnIce have split this number into two separate categories: dCFImpact and dCAImpact. This allows us to see if a player is getting that big impact number as a result of strong offensive play or as a product of good defensive possession work. The following scatter plot shows the dCFImpact and dCAImpact of the rookies thus far this season.

dCFimpactdCAimpact
dCFImpact vs. dCAImpact for the 8 rookies in my analysis. All data extracted from war-on-ice.com on February 17, 2015.

A positive dCFImpact number is good, and a negative dCAImpact number is good. The best players, or most well-rounded, should fall in the lower-right quadrant of the graph. This would mean they are driving both more possession for than expected and less possession against than expected. But really what this plot shows is where their dCorsiImpact number is being derived from.

Once again, Anders Lee and Mark Stone are looking good here, while my previous prediction (Filip Forsberg) isn’t faring to well. While he is good offensively, he does not meet his expected CA60 number and this effects his dCorsi60 and dCorsiImpact numbers accordingly. Lee is able to drive huge offensive numbers compared to the others, with a dCFImpact of 75.41. This is over twice as large as any other rookie in this group. Stone is strong defensively, posting a stronger dCAImpact number than Lee which allows him to gain some ground back in terms of total dCorsiImpact. Stone is a strong defensive force on the Sens this year, and is clearly performing the best in allowing possession against out of all forwards in this group.

But even with the strong numbers from these forwards, I am still so impressed with the numbers that John Klingberg is posting. In my initial analysis at HP, I was really close to pegging him as my favourite. After this finding, it is clear: my [revised] selection for the Calder Trophy in 2014-2015 goes to John Klingberg. After more research and analysis, I had to adjust my prediction. This guy is getting big minutes on a Stars squad that is looking to force its way into the playoffs. Klingberg will have to be a driving force behind this run if they want to have a chance, and if he keeps up his production thus far, their chances aren’t so bad. With the injury to Seguin, they may have to get some luck elsewhere, but I am confident this guy will be able to contribute to the team and help them get where they want to go.

Klingberg’s 5.36 dCorsi60 number is impressive, but with his big minutes, it drives his dCorsiImpact more than other skaters here. His total impact number isn’t driven by just one component (like Anders Lee’s); it is composed of a strong dCFImpact and a strong dCAImpact. This rookie d-man is driving and preventing possession better than expected, and this definitely warrants him as a candidate for the Calder Trophy.

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Calder Trophy Race Analysis: dCorsi and Usage Comparison

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