Wednesday, September 17, 2014

What comes next for the hockey analytics movement?

This time last year, mentioning the word “analytics” in hockey circles was a good way to bring any conversation to a screeching halt. At best, you might get blank stares. At worse, you could expect a scowl, followed by a clich├ęd lecture about spreadsheets, protractors, and just watching the damn games.

Those days now seem like a very long time ago. In what became known as hockey’s summer of analytics, several of the community’s top minds were snapped up by NHL teams. Fan forums and Twitter lit up with those wanting to learn about these newfangled numbers. Talk radio was debating the merits of Corsi and Fenwick, and even old-school media began incorporating the newer stats into their work. Suddenly, analytics is everywhere.

All of this has left the field with new credibility, as even longtime critics have been forced to concede that there’s value in analytics. But it’s also left behind a void, with thought leaders like Tyler Dellow and Eric Tulsky now largely silenced by the terms of their new employment.

On Saturday, several of the field’s top remaining names gathered in Calgary for the second Alberta Analytics Conference. The event was organized by Rob Vollman1 and attended by roughly 70 fans, as well as media and at least one team executive.2

As you’d expect, the day featured the occasional mention of how much the tide had turned, and maybe even a little bit of gloating. But for the most part, the focus was on the future. Hockey analytics has arrived and is here to stay. But compared to sports like baseball, the field is still in its infancy. Despite the progress of the last year, there’s a long road ahead, and lots of ground still left to be covered.

So where do we go from here? Here are five areas you can expect to hear more about over the coming months and years.

All the small things

The best known of the new wave of hockey stats is Corsi, which measures the number of shots that each team attempts. Corsi3 turns out to be hugely important — it’s one of the best indicators we have of future success, especially at the team level. Put simply, teams that can gain an edge in possession and create more shot attempts usually go on to beat the teams that can’t. As far as analytics go, this is settled science and has been for a long time.

Great. So now what?

After all, any coach who looked at the numbers is going to want to know: If Corsi is so important, how do I improve my team’s number? “Be a better possession team” isn’t a useful answer. “Create more Corsi events” is even worse. All of this stuff may be useful for predicting future success and failure at a macro level, but as a practical matter it isn’t useful to coaching staffs unless it can translate into specific changes to a team’s strategic approach.

We covered one example last season: zone entries. At last year’s Sloan Conference, Tulsky and others presented a paper that looked at the value of entering the offensive zone with possession, as opposed to dumping the puck in deep and then trying to retrieve it. They found that entry with possession was roughly twice as valuable in terms of generating shots and scoring chances. That went against conventional North American hockey wisdom, which has long leaned toward the safer dump-and-chase approach, but the numbers were convincing. It was also exactly the sort of insight that a coach can actually use, and in fact, some NHL coaches did.4

Now, analysts like Justin Azevedo are looking for similar breakthroughs. On Saturday, Azevedo presented his efforts to study what he refers to as microstats, the sort of common plays that take place on virtually every shift, but that aren’t tracked separately in the box score. Azevedo wants to know whether the way teams approach those common plays could impact their Corsi.

For instance, think about the stretch pass. Hockey fans have come to appreciate the ability of a defenseman to make a long pass across multiple zones to a streaking forward; it’s one of the most coveted skills that an offensive blueliner can have. But how often do stretch passes succeed? And do the failed attempts, which can often result in an icing call or, worse, the play quickly coming back the other way, hurt a team more than the successful ones help?5

Those are the sort of questions that will become more common as fans like Azevedo figure out what’s worth tracking. It’s daunting work; unlike shot attempts, the data can’t be scraped from the NHL’s logs, so it has to be tracked manually by somebody watching the game and recording each play they see. It’s hard for one person to track more than one team at a time,6 and much of the work is subjective and prone to error.

It’s a tough job, but it’s the sort of thing that will have to be done if analysts want to answer that coach’s question: Great, now what?

>> Read the full post on Grantland


  1. " They found that entry with possession was roughly twice as valuable in terms of generating shots and scoring chances."
    Is the reverse true?
    Do the the safer dump-and-chase approach generate more shots for the opposing team? Maybe not if that team is dump and chase too. But maybe it generates more shots for the entry-with-possession teams.

  2. other than the fact that they did not shoot enough, it seems to me that the Russian teams of the 70s-80s were already applying a lot of the lessons that teams will now learn from using advanced statistics. especially on the puck possession/zone entry

    1. They certainly seem to have had the zone entry problem solved. On the other hand, there were things like pulling the goalie strategy that they had completely wrong.