Flyers Insider for NBC Sports Philadelphia, John Boruk, shared this tweet on Saturday morning.
Capitals are prime example why Corsi/Fenwick don't make sense. They've outscored their opponent 20-14, but they've been outshot 170-127
— John Boruk (@johnborukNBCS) October 14, 2017
As a critique of shot-attempt statistics, this is incorrect. As an analysis of the Capitals, this is clumsy. As a work of responsible journalism, this is a failure.
Yes, the Capitals have indeed been outshot 170 to 127, for a shots-for percentage of 42.8, but that’s not Corsi or Fenwick, the stats Boruk is decrying.
Corsi is all shot attempts (including misses, blocks, and shots on goal) and Fenwick is all unblocked shot attempts (including missed shots and shots on goal). Here’s a quick rundown:
Shots on goal
Shots on goal and missed shots
Shots on goal, missed shots, and blocked shots
(I made a short video about this a few years back if you’re a visual learner.)
If Boruk used unblocked attempts (Fenwick), the number would be 240 to 187, or 43.8 percent. If he used all shot attempts (Corsi), the number would be 312 to 253, or 44.8 percent.
(Note that the number gets close to 50 percent the bigger the sample gets. That’s a good illustration of why analysis is stronger with a bigger population of data: sample-size distortions become less common.)
Anyway, Boruk’s not talking about what he says he is talking about. And even if he were…
Shot-attempt numbers are almost always isolated by the game state: power play, penalty kill, or even strength. This is done to get a better description of each circumstance independently, and also to avoid distortions in a combined number. Either Boruk doesn’t know this, or he does know and fudged his sample to suit his argument.
In truth, more than thirty percent of the Capitals’ opponent’s attempts have come during the penalty kill, during which the Capitals have struggled so far.
By conflating these numbers, Boruk obfuscates the truth, which is a curious choice for an analyst whose job is to explain.
No one reasonable expects a team’s shot-attempt percentage to be perfectly proportional to their goals percentage over a small number of games. The former is a measurement of trying to score, and the latter is a measurement of actually scoring. The distinction between the two is finishing, measured in shooting and saving percentages.
The gap between the Capitals’ attempts percentage and goals percentage is telling. At 5-on-5 the Capitals are scoring on 15.7 percent of their shots, and their opponents are scoring on 6.5 percent of their shots. Both of those numbers are out of whack, and we should expect them to normalize as the season grows – but not to the same degree. While 15.7 is very high shooting, the Caps goalies’ 93.5 percent saving is not out of bounds for Braden Holtby and Philipp Grubauer, who saved 93.7 percent last season. Braden Holtby is notorious for being right around 93 percent every year.
But the difference between the Caps’ goals and attempts numbers are not at all remarkable over a five-game sample.
With 20 goals and 14 opponent goals, the Caps have a 58.8 percent goals-for percentage. That’s really high – even though it’s lower than last season’s 59.6 percent. But by looking at the underlying numbers (Washington’s 46.4 percent of shot attempts during 5-on-5), we have reason to believe they won’t be able to repeat last season’s success – though the confidence of our belief should be strongly tempered by the tiny, tiny sample size.
Put another way: the Caps’ low shot-attempt numbers so far suggest that they won’t continue to score nearly 60 percent of goals in the future. So, really, Boruk’s critique of shot attempt stats actually serves to reinforce their usefulness.
Attempt-based statistics get a bad reputation, and this is a good example why. Boruk either does not understand them and demonizes them out of his ignorance, or he does understand them but misrepresents them deliberately. I’m not sure which of those two would be worse.
With a little due diligence, the shot-attempt stats make a lot of sense and reveal enlightening information about the Capitals. So far this season:
I don’t know if I count as a professional hockey writer. I make money from it, but it’s not a lot, and this is not my day job. I’m not a member of any professional association, but I am bound by my own set of guidelines for good conduct. To me that means increasing the amount of useful information in the hockey universe. If I have any duties, they are to my audience, and in serving them honestly. That duty requires me to do a good bit of self-education, but it also affords me the opportunity to share what I’ve learned with other people. I relish that role and I take it seriously.
Russian Machine Never Breaks is not associated with the Washington Capitals; Monumental Sports, the NHL, or its properties. Not even a little bit.
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