Friday, September 16, 2011

Bob McCown on "puck luck"

I just got a copy of "McCown's Law -- The 100 Greatest Hockey Arguments." I'm only on number 1, but already Bob McCown nails it:

" ... hockey is enveloped by a culture that demands that everything be rationalized or explained ...

... it's hilarious the way fans react when their team loses a close game. You'd swear the players couldn't do anything right. And yet, when the same team wins a game by a one-goal margin, it's showered in platitudes.

So here's an experiment I'd love to perform sometime.

Let's take the tape of a five-year-old NHL game -- any game -- in which the score ended 3-1. Now, let's edit out the goals and leave all the rest, so that about 59 of the 60 minutes are there to watch.

Now show it to an audience of hockey fans and see if they can guess who won.

I bet they couldn't, because aside from the moments in which the goals are scored, an awful lot of hockey games are nothing but back-and-forth flow, the trading of chances and puck luck.

To have some fun, let's try the same experiment with a bunch of reporters. Then, let's show them the stories they wrote about that exact game.

Most nights in hockey, both teams skate hard, check hard, and go to the net ... And one of them has a puck hit the post and bounce into the net. And the other hits a post and watches it bounce wide. On more nights than you'd believe, the difference is as simple as that ...

In fact, I would say that puck luck, as it is often called, decides roughly half of the close games in the National Hockey League."

Absolutely right.

I'm looking forward to the rest of McCown's book. I'll probably find more things to post about later, if the quality of the first chapter is any indication.


Well, one picky point on McCown's essay: I don't know what "decides roughly half of the close games" means. If a team wins 2-1, what does it mean that luck decided it, or not? That's a bit vague. I know what McCown means to say, and I agree with it on a gut level, but ... I'm not comfortable with phrasing it that way, because I like to have a precise definition.

So let's arbitrarily make one up.

Suppose you did something like what McCown suggested -- you edited a tape of the game to remove the results all the shots and "dangerous" scoring chances (that might or might not have resulted in shots). Then you somehow computed the win probability based only on the situations that appear on tape. Maybe you give a breakaway an expectation of 0.3 goals. And for a point blank slot possession, you assign 0.5 goals. And a slapshot from the point, 0.1 goals. And so on.

You compute an expected score based on that.

Then you look at the real score.

1. If the "wrong" team won, it must have done so by "puck luck".

2. If the "right" team won, but its expectation was to win by less than one goal, then you define that as a win by "puck luck".

That might actually be possible to partly figure out. The NHL website gives all the shots, by distance and type, and Alan Ryder has done lots of research on how to get scoring probabilities for shots. However, the NHL doesn't list other kinds of scoring chances aren't listed, so you'd have to stick to *shot* "puck luck".

In any case, even if you had scoring chances, there would still be luck unaccounted for, in the development of the play. A breakaway might have itself been caused by a defender missing an easy puck. A good chance was caused by three low-odds passes that happened to click. And so on.

So, let's try again. How about, a game is decided by "puck luck" if:

You edit the game per McCown's suggestion, and show it to reporters. You make them bet their own money on who won, against each other at odds that they negotiate. If the overall odds wind up between 60:40 and 50:50, or the overall underdog won the game, then that's a game decided by "puck luck".

I'm not suggesting you actually do this, but that you do a thought experiment and estimate what would happen. There are obviously some games where one team absolutely dominates (and wins). The reporters would obviously get the right answer here ... they'd need 90:10 odds or something to back the underdog. But there are obviously games that would look like toss-ups.

Any other suggestions for how to define that in a way where we could actually talk about how to get an answer?


As an aside, I think this kind of "replay" technique has all kinds of sabermetric applications. To evaluate referee performance, take a tape of the foul, do some digital processing to obscure the players and teams involved, and get referees to judge it. To scout a pitcher, you can avoid being biased by the result of the pitch (a good pitch can still be hit for a home run) by digitally removing the result (and perhaps extrapolating/animating the last few inches, if the pitch was actually contacted). And so on.

I think I proposed this thought experiment once, along the same lines. Suppose you had a time machine. You go 40 years into the future, and you go to, and you download video of every inning of every game.

You take 10 players across the spectrum of hitting talent: the equivalent of Albert Pujols, the equivalent of John McDonald, the equivalent of Ichiro Suzuki, and so on. You carefully select 200 AB from each of them, so that those 200 AB show the same batting line for each player, and put them on tape.

Then, you bring those tapes back to the present day, and show them to all the scouts. Would the scouts be able to tell the good players from the bad players?

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At Wednesday, September 21, 2011 12:46:00 PM, Blogger Vic Ferrari said...

Having listened to his radio show, I'm a bit surprised that McCown is that insightful.

McCown's idea of editing out the goals is terrific. The narrative of the game after the fact is always written from the score backwards, lady luck rarely gets her due credit.

Another way to look at it is to view a game and keep a tally of every shot directed at the net, and ballpark it's chances of going in as a percentage. So maybe you think a snap shot from inside the scoring area, but near one of the dots ... feels like about a 10% chance of going in. A slapshot from the point with traffic in front, from a D with a heavy shot ... maybe 3%. A forward hacks at a rebound just outside the crease, looks like about 20%. If a person looks at even just a couple of games through that lens ... the role of chance in the individual games becomes obvious and enormous. Or so I think.


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