Does Defense Win Championships?

With hockey underway again I’ve been spending a lot of time hanging around the local arena watching my kids play, and an old mantra keeps springing up – “Defense wins championships”. A widely held belief is that defense wins championships and in hockey the way to win is to build from the net out. Upon hearing this, my first thought was that I’ve actually read something on this before and I went to track down where. I remembered that this cliché isn’t necessarily true, even if it seems logical.

Tobias Moskowitz and L. Jon Wertheim have a great book titled “Scorecasting: The Hidden Influences Behind How Sports Are Played and Games are Won” (info on this book can be found via their website: http://scorecasting.com). It’s a nice book for those interested in using data to better understand sports, and is full of chapters where the authors go out and empirically test beliefs widely held among sports fans. One of these is whether defense wins championships. The authors examine all 4 major North American sports (NHL, NBA, MLB, NFL) and find that defense is no more important than offense. Winning games requires either great defense or great offense, and if you are really lucky…both!! More on this work (as it pertains to the NFL) can be found on a guest spot they did for Freakonomics (http://freakonomics.com/2012/01/20/does-defense-really-win-championships/).

Reading this book led me to search for more on this topic, specifically as it pertains to hockey, and I came across a great website that marries hockey with data. The Department of Hockey Analytics (http://www.depthockeyanalytics.com/) is a website developed by IJay Palansky, Phil Curry, and Ian Cooper. Their recent article in the Toronto Start “In the NHL, Defence Doesn’t Actually Win Championships: Hockey Analytics” pretty much answers the question right in the title. http://www.thestar.com/sports/hockey/2014/05/29/in_the_nhl_defence_doesnt_actually_win_championships_hockey_analytics.html

The authors look at this question a few ways, and I’ll leave the details of this article to the reader, but two things stood out for me. First, when looking at who won the Stanley Cup since 1980, 5 times the team with the number one defense during the season won, while 5 teams with the number one offense won. So no clear winner here in terms of defense vs. offense. Second, using a probit analysis to estimate the impact of defense and offense on winning semi-final and final playoff rounds from 1980 to 2013, the authors found that offense contributed more than defense to the likelihood a team would win (defense does matter, just not as much as offense).

So what’s the take away from all of this? Well two things. First, with this question specifically, defense is important, but so too is offense, and neither really dominates the other. As Palansky points out, goal differential is what wins and this can be achieved by scoring lots or giving up little. Second, is the broader issue of sports mantras. We hear them all the time, but the next time you hear one presented as fact, ask yourself…I wonder what the data says about this!

RAC

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