A mini-firestorm was started in the hockey blogosphere earlier this week when Maple Leaf Hot Stove published an interview with Toronto Maple Leafs assistant coach Greg Cronin in which he claimed that shot quantity is "misleading" and that the Leafs would rather focus on gaining long shifts in the attacking zone. He specifically cited the number "40 second[s]" which a lot of people jumped on. I think he was speaking generally there (I doubt the coaches specifically target 40 seconds), but that has lead to questions about how often a team is actually able to control the puck in the offensive zone for that length of time.
As it happens, I have a decent amount of data on that. Between November 15 and December 5, 2011 I tracked the time that teams had possession of the puck in the offensive zone during 10 Leafs games. I wrote up a summary of my results in this post (in addition to game-by-game breakdowns that I wrote as I tracked them). I had been planning on avoiding doing any hockey blogging this summer, but since to the best of my knowledge no one else has ever tracked this kind of information I figured I should probably put together a post using the data that I have.
What exactly did I track? I'll quote myself:
I decided that I would track how long each team had possession of the puck in the offensive zone. Because it would be virtually impossible to track each minor puck movement, I decided to use a bit of a simplified measure - I counted the beginning of an offensive zone possession as the time at which the attacking team first gained clear possession of the puck once it was in the offensive zone, and I counted the end of the possession as the time at which either the puck left the zone, or the defence was in clear control of the puck and not under significant pressure from a forechecker. Obviously there's some subjectivity involved in that, but given how quickly the game moves I think that was a good compromise between good data collection and mental sanity. As I discovered while recording time on attack, even that somewhat loose definition of a possession can be difficult to track in real-time, but I think the results I've gathered are on the whole pretty reliable.
Using this method I collected the length of 1090 individual attacking zone shifts over the course of those 10 games (all numbers here are for even strength shifts only). Now, clearly 10 games isn't that many given that there are 1230 played over the course of a full NHL regular season, and the only team I have more than 2 games worth of data for is the Leafs. That said, 1090 shifts is a fairly sizeable number, and I think the results here are good enough to at least draw some broad conclusions. Also, given that this is actual time with the puck, I think this data really gets directly at what Cronin was talking about.
I've divided the results into three categories: Leafs, Leafs' opponents, and total. Let's start by looking at some aggregate numbers:
|Team||# of Shifts||Avg Shift Length||Median Shift Length|
The really telling stat here is the median; more than half of all attacking zone shifts are well under 10 seconds. As I said back in my original summary of this data, this helps explain why zone entries are so important which is that a huge portion of the game is spent in transition. That's why a guy like Jake Gardiner, who can make a great first pass out of the zone and skate the puck out of trouble, is far more valuable than a "stay-at-home" defenceman; the stay-at-home guy doesn't actually get a lot of opportunities to stay-at-home. You really can never have too many puck moving defencemen.
Next up I've got some more detailed breakdowns of the data showing the number of individual shifts of a certain length that the Leafs and their opponents had. First up is Toronto:
|Length||Number||% of Shifts|
|10 – 19||156||29.1%|
|20 – 29||44||8.2%|
|30 – 39||15||2.8%|
|40 – 49||7||1.3%|
|50 – 59||0||0.0%|
And their opponents:
|Length||Number||% of Shifts|
|10 – 19||175||31.6%|
|20 – 29||51||9.2%|
|30 – 39||18||3.2%|
|40 – 49||8||1.4%|
|50 – 59||2||0.4%|
Not only is an attacking zone shift of 40 seconds exceedingly rare, but attacking zone shifts of just half that are very uncommon. Over the course of 10 games Toronto's opponents average 1.5 attacking zone shifts per game of 40 seconds or more and Toronto averaged less than one per game! As to whether this is just dumb luck due to the sample size or whether Toronto was just really bad defensively I couldn't say for sure. It does look to me like Toronto may have had a harder time clearing the zone than their opponents did (this is under Ron Wilson, by the way), but even still, that amounts to just a few shifts a game, not something you could reasonably base your entire coaching strategy on.
So, to sum up: most shifts in the attacking zone are very short, most of the game is spent in transition, long sieges in the offensive zone are very rare, don't sign guys who can't move the puck.