Mar 162011
 

I have posted a few articles here recently about the existence of shot quality, one of which related to last seasons Washington Capitals and one related to how shot quality varies according to game score but there are still shot quality deniers out there.  One of the comments I received from a shot quality denier to those posts was as in depth as “You did it wrong” but offered no further explanation.  So there it stands.

Derek Zona and Gabe Desjardins over at Behind the Net Hockey (mostly shot quality deniers) have put up a $150 prize for anyone who can show that shot quality exists.  One method they suggested one could pursue to prove such a thing was the following:

Are there players or teams with the ability to drive or suppress on-ice shooting percentage?  What are their characteristics?

This prompted Rob Vollman (who I presume is a shot quality denier, my apologies if not) to look into just that and to do so he identified a group of players who had the highest save percentage against while they were on the ice.  The theory is, if shot quality suppression was a talent then there should exist players who experience a very good save percentage for their team while they are on the ice.  The group of players identified varied significantly from George Parros to Kyle Wellwood to Sean O’Donnell to Marco Sturm.  In the end Rob came to the conclusion that these players all had high save percentages while they were on the ice because they mostly played against weaker quality of competition.

But none of them are facing their team’s toughest minutes.  If they truly had the ability to suppress shooting percentage, why would Kesler and Burrows hop out against Ovechkin instead of Malhotra?  Why would Pronger keep an eye on Crosby instead of O’Donnell?  Kudos to each of them for playing their roles very well, but the explanation still appears grounded in Quality of Competition.

And there is the fault in logic.

  • Claim:  Shot quality doesn’t exist.
  • Counter-evidence:  Some players do experience higher save percentages while they are on the ice.
  • Rational:  They do so because they play against weaker quality of competition.
  • Claim Confirmed:  Phew, my claim that shot quality doesn’t exist remains valid.

Now the whole problem with that theory is the rational part because the rational part requires shot quality to be real for it to be true.  The only way you can have a better quality of competition (in terms shooting/save percentage) is to have shot quality exist.  If shot quality didn’t exist all competitors would have the same level of shooting percentage talent.  The claim and rational can’t both be true, so the logic fails.

And that is where identifying shot quality becomes difficult.  Players that are generally good at reducing the quality of shots against are lined up against opponents who are generally good at creating quality shots for.  The net result is their talents cancel each other out to some extent making it difficult to identify shot quality driving/suppressing talent just by looking at the numbers in isolation of who they are playing with and against.

  7 Responses to “The Odd Logic of a Shot Quality Denier”

  1.  

    Not sure that’s true. We know most good offensive players create lots of shots (special players like Kovalchuk and, I’d guess, Vanek, are exceptions). It makes sense, then to have the guys who suppress shooting% the best to match up against those guys, right?

    You did do a regression and found shooting% correlates better with goals than shots for. If these players’ coaches believed that to be true, they’d use guys like Sturm and Parros against top lines, since suppressing shooting% contributes more to having fewer goals against (I would think) than shooting quantity.

    Instead, most teams using guys who suppress shots against, but not necessarily goals against, to play against other top lines certainly supports quantity over quality.

  2.  

    There’s a big gap between showing that individual players are more likely to score a goal on any given shot – which is obviously true and I’ve seen nobody deny – and proving that there’s a substantial difference between individual teams at the NHL level in terms of their ability to influece shot quality.

    My personal belief is not that shot quality doesn’t exist, but that it’s overstated as a means of discreditting shot metrics and confirming narratives (i.e. the Montreal Canadiens went on a deep playoff run last season because of their team-togetherness and bend-don’t-break defensive system).

    I’d think if shot quality did exist at the team level in a meaningful way (i.e. one team’s systems in all situations can control it to a degree), the most logical place to look would be teams coached by Jacques Lemaire, by comparing pre-tenure and post-tenure with during. I haven’t seen that evidence.

    Meanwhile, trotting out a triumphalist ‘shot quality denier’ post exactly one day after writing an interesting article on shot quality in game situations is rather bad form, wouldn’t you say?

  3.  

    “There’s a big gap between showing that individual players are more likely to score a goal on any given shot – which is obviously true and I’ve seen nobody deny – and proving that there’s a substantial difference between individual teams at the NHL level in terms of their ability to influece shot quality.”

    But we know teams can influence shot quality. If they can’t, how do you explain save/shooting percentage variances across game situations. It actually astonishes me that people would deny something so obvious. Now there are certainly a lot of situations where things just average out or the fact that there may be a large number of ordinary teams have very little difference in talent levels, but to deny shot quality exists just seems outlandish to me. Maybe I am out to lunch here, but unless someone can explain to me how shot quality (and quantity) can vary across game scores, without teams being able to control shot quality I have to believe shot quality exists and can be controlled at a player and team level.

    “Meanwhile, trotting out a triumphalist ‘shot quality denier’ post exactly one day after writing an interesting article on shot quality in game situations is rather bad form, wouldn’t you say?”

    Bad form? Not sure. I’ll let my readers decide that, but pointing out an invalid logic argument on a blog that claims to want to understand hockey through advanced statistical analysis and also which regularly criticizes others for illogical or invalid claims/arguments seems perfectly fair to me.

  4.  

    No one denies shot quality exists. The issue is whether, *ceteris paribus*, teams systematically take or allow higher quality shots than other team, and to a *significant* degree. The whole game-state deal has been labeled “score effects.” It is shot quality, but not the oft-cited shot quality that most stats hockey bloggers tend to downplay the importance of.

    Moreover, I’m not sure different teams go into proportionally more defensive schemes when up or more aggressive schemes when down. I’d think each team gets better/worse at generating shots a similar amount by game state (i.e. I wouldn’t expect Vancouver to get 50% better down 1 while Washington only gets 10% better).

    •  

      The point is, teams (and players) can and do control shot quality. They certainly do it based on the score of the game and I showed that the high Washington Capitals shooting percentage from last season was far beyond what one would expect from luck alone. There are people who deny this.

      It is true that, on a team level, the majority of teams are within the ‘margin of luck’ if you will, at least over the course of a single season. i.e. The majority of teams you cannot find a statistically significant difference over the course of a single season. This is because the majority of teams play similar styles and the majority of teams have similar overall talent levels. But there are exceptions, such as the Washington Capitals of last season.

      On a player level, I think players can drive or suppress shot quality, it is just difficult to identify because those that are good at driving shot quality (and are trying to do so) play against those that are good at suppressing it (and are trying to do so). The effects cancel each other out making both sets of players (drivers and suppressors) appear ordinary. To some extent this may happen on a team level too.

  5.  

    I got proof and I want my $150 $’s…His name is Vladimir Zharkov
    GP G A PTS SH Sh%
    2009-2010 Devils 40 0 10 10 54 0.0
    2010-2011 Devils 38 2 2 4 40 5.0
    NHL TOTALS 78 2 12 14 94 2.1

    He’s got outstanding Corsi #’s and ferry winkles…but he couldn’t see net if the goalie fell over and has hands like bricks…you can check out the video highlights yourself

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