Written by Jibblescribbits | 11 Mar 2014

This is a pretty contraversial opinion in Avs land, so I better have a pretty good reason and logic to back it up. And I do. 

First of all, It's important to note how important Puck Possession (measured with either Corsi or Fenwick) is to a team's success. I don't want to go into a long schpiel on it, but Eric T, one of the best analytics minds in hockey right now, has it somewhere between 3-5 times more important than shot quality or goaltending. But it's not just analytics guys, take recent Stanley Cup Winning Coach Daryl Sutter's words for it, from the Blog Nichols on Hockey (emphasis mine): 

Via The Edmonton Journal, Sutter says the Kings’ seemingly defend-first game is a “misconception. The big thing in today’s game is you have to be able to forecheck and backcheck, and you have to have the puck. You can’t give the puck up. We don’t play in our zone, so there’s not much defending."

Also: “I’ve coached in three decades now and this stuff where they said Marian had to play in Jacques’s system is a bunch of bull-crap. The game’s changed. They think there’s defending in today’s game. Nah, it’s how much you have the puck. Teams that play around in their own zone think they’re defending but they’re generally getting scored on or taking face-offs and they need a goalie to stand on his head if that’s the way they play."

In other words: to be successful a team needs to have the puck or get brilliant goaltending. While coaching can affect goaltending (And I think Roy deserves a ton of praise for his work turning Varlamov into a reliable goaltender, potentially a Vezina winning one) The real place a coach can have an impact is on puck possession, and shot quality (which, again, is not as important, but not necessarily negligible). So, in my eyes a good team will have a good Corsi when the score is close 

The Avs Corsi-close, according to the indispensible ExtraSkater.com: The Avs are 25th, with a Corsi of 47.7%, which is pretty awful. Roy's coaching isn't doing very good for the one thing that he has the most control over. 

Now, this is where the argument comes in that his system forces teams to shoot from the outside and those are low quality shots. c6hor8 of Mile High Hockey makes the point pretty eloquently in this comment (i'm excerpting here. It's a good analysis of Xs and Os so I'd recommend heading over and reading the whole thing):

...

Also, Roy employs something I like to called “controlled possession.” Possession works in two way: 1) having the puck on your stick or 2) having the puck on someone else’s stick but controlling where he goes. The latter is one of the hallmarks of man-to-man coverage. It prevents passes, it prevents space, and it allows the defending player to control (if done well) the puck carrier. Clearly a better defense will take possession more and use the 1st type more than the 2nd. Over time man-to-man coverage is high risk/high reward so issues will arise and more so than in a standard zone coverage.

...

In fact, in the 32 shots the Avs usually give up I would estimate 25 of those are so routine that most starting goalies save them. It’s the other 7 that need to be stopped and toned down. Those 7 or so are the ones they score on, the ones that look dangerous, and the ones a better defense will prevent or make like the other 25. Varly has played great because he has made those 25 or so saves AND made the other 7 when asked. And those have been great saves. This system is the nemesis of Corsi because it can’t be applied accurately. It looks are something in aggregate when that only tells part of the story. I would argue that the first 2 months of the season looked more like relying on Varly and recently the Avs have discovered their controlled possession system and use it to gain their own possession, move the puck up the ice, and let their impressive offense flourish. 

According to this explination, and other similar ones, if what he's saying is correct, The Avs would force a higher percentage of lower quality shots than other teams. This has been an argument for every team whose had unsustainably good goaltending covering bad defense since Corsi emerged. Luckily, recently, more analytics tools have emerged to test this. 

Using Ninjagreg's new site I was able to compile a data base for every team, through March 7th, of where the shots they were giving up are and find out which teams give up a larger % of their shots from close in. If c6hor8 is right, The Avs will be giving up more shots from the perimeters and less shots from the slot and right in front of the net.

This is Proportion of Shots Against within 30ft and 20 ft (by percentage) for away data (to remove any home scoring effects) Here's the full data set in a Google Doc and I'll post a truncated version here for formatting sake:

	< 20 ft %	< 30 ft%
Minn	19.32%	31.40%
Tampa	21.10%	38.23%
Edmonton	21.83%	37.85%
Toronto	21.96%	33.05%
San Jose	22.98%	37.28%
Vancouver	23.00%	44.94%
Boston	23.21%	37.44%
Detroit	24.55%	38.91%
Nashville	24.58%	39.00%
Philadelphia	24.82%	35.06%
Buffalo	24.94%	37.59%
Washington	25.30%	39.01%
Florida	26.04%	42.49%
Columbus	26.64%	40.03%
Phoenix	26.78%	39.30%
StL	26.83%	44.92%
Montreal	27.59%	41.14%
Ottawa	27.67%	40.91%
Calgary	27.72%	43.85%
NJ	28.26%	44.72%
Chicago	28.77%	44.63%
Carolina	29.19%	41.75%
LA	29.57%	41.39%
Pittsburgh	29.73%	43.79%
Winnipeg	31.22%	45.63%
Colorado	33.42%	43.85%
Dallas	33.79%	48.56%
Anaheim	35.03%	52.29%
New York Rangers	37.67%	52.52%
New York Islanders	39.58%	58.08%

 

In the spreadsheet there's the Average and St. Deviation, which gives a more complete set of data. If you take the standard deviation into effect (something we in the analytics community don't do enough) here's what it means about the Avs:

• There's a 50% chance the Avs give up a lot more high quality shots than the opposing team
• There's a ~68% chance the Avs are no better than slightly below average at restricting shot quality
• There's a ~98% chance the Avs are no better than above average at restricting quality shots.

I'm not trying to argue the Xs and Os of c6hor8's system, but the effectiveness that is being attributed to it is extremely unlikely, given the data. 

I think the data makes me conclude a few things: Roy's system is more likely to rely on a goaltender making tough saves, which makes Varlamov's season all the more exemplary (and Roy deserves some coaching Kudos for Varly's turnaround). But it also makes me think Roy's system isn't very effective (or, more likely, the players who run Roy's system aren't very effective). You can call it random chance or great goaltending, or likely both, but it's the combination of the two that is fueling the Avs standings success.

More takeaways:

• Todd McLellan should tentetively be the Adams'winner, with a sparkling Corsi AND a sparkling Shot quality against, the sharks are going to be really tough to play against in the playoffs. 

• Cooper from TBL is the other Adams candidate and his system, unlike Roy's, is likely helping fuel Bishop's success this season. With him losing Stamkos I'd consider changing my non-existant vote. 

 

Even with all of this here, it's still likely that Corsi-close is, and goaltending likely is, a bigger driver of W/L/Points than the data above. Edmonton has pretty good numbers, but are so over matched in Corsi and top it off with miserable goaltending that any advantage they gain here is lost multiple times over. Toronto has good numbers here, and good goaltending, but is a miserable Corsi team. They're still a minus in goal differential on the season (and down 5-1 tonight as I write this).  

Unfortunately, I can't pull out who the best at creating chances is yet, it's entirely possible Roy's system gives up chances in favor of creating scoring chances at the other end, but since the website I pull from updates regularly I have to record all the data on the same day, which is an effort. The next analysis will be doing just that, but for now: Roy's sytem gives up a ton of shots and gives up quality shots disproportionally when compared to other teams.