Optimal Even-Strength Shift Length, 2008-09
by Hawerchuk on Feb 11, 2010 9:00 AM EST
21 comments
Tyler Dellow had a nice post about average shift lengths, and how the leaders almost all play in the Eastern Conference. To quote Tyler: "it seems to me that being on the ice after a minute is sort of like being in a bar after 1:00 a.m. - there’s no guarantee that something bad will happen, it’s possible that something good will happen but the odds are slanted heavily in favour of something bad..."
And indeed that is true of Corsi percentage - the percentage of total shots that are shots for:
The small uptick for 0-6 seconds is from the attacking team's defensemen jumping over the boards on an offensive rush. The defending team had better not be changing when the puck is coming into its end! At any rate, the break-even point is around 40 seconds, which is roughly the average even-strength shift length league-wide, and things fall apart after that.
By 70 seconds, only 40% of total shots are shots for. To put that in perspective, only the absolute worst players in the NHL have shot totals at that level - 40% for, 60% against. Staying on the ice even just a bit beyond a minute usually turns the average NHL player into a defensive catastrophe on the scale of Wade Belak. Shifts like this are relatively rare, but most players seem to have one egregiously long one per game, with, as you can see above, mediocre results.
The story is clear when you combine the results over longer periods of time:
| Time on Ice | Corsi % | Shot % F | Shot % A | Ratio |
| 7-15 | 51.2 | 8.0 | 7.7 | 1.04 |
| 16-30 | 52.2 | 8.5 | 8.3 | 1.02 |
| 31-45 | 49.5 | 8.7 | 8.6 | 1.01 |
| 46-60 | 46.2 | 8.4 | 8.8 | 0.95 |
| >60 | 39.7 | 9.3 | 10.1 | 0.92 |
So as shifts get longer, not only do shot totals take a wrong turn for tired players, but the quality of the opposing team's chances goes up too. Bottom line: as Tyler said, nothing good is going to happen once you've been on the ice for a minute.
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Interesting stuff.
One thing I find curious… how would you explain the fact that Shot % goes up for players on the ice more than 60 seconds? Is it because most players that regularly stay on the ice that long are high shot % players (ie: Ovechkin, Kovalchuk…) ?
I’m inclined to believe there are a few variables at play here. For one, the number of shifts that last longer than 60 seconds is probably quite small in comparison to those in the 0-40 second range, so the smaller sample size will amplify the effects of outliers.
I think you’re also right in speculating that some of the variability is due to star power. There are probably 2, perhaps 3 players on a team’s bench who you’d be ok with taking a 100 second shift in a certain situation. My guess, is these are most often star players, and it occurs most often late in games when the team is looking to tie things up, or defend a narrow lead.
Purely conjecture on my part, but I suspect it holds water.
by iwearstripes on Feb 12, 2010 12:57 PM EST up reply actions
Your body's energy
There is also some stats out there about your body’s systems and how once you are on for too long your body starts tapping into different energy systems. It is better to go hard for under a minute, then recover.
Check out my Hockey Tips blog for some great tips and tricks you can use to improve your game
by HowToHockey.com on Feb 11, 2010 9:32 AM EST reply actions
Is there any correlation between depth and length of line shift? I would imagine so, but it would be interesting to see.
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by Bettman's Nightmare on Feb 11, 2010 9:54 AM EST reply actions
By “depth,” I mean depth of talent among the forward lines.
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by Bettman's Nightmare on Feb 11, 2010 9:55 AM EST up reply actions
I’m surprised that the Corsi% is even that high (~30-40%) at the ~100 second mark. From my sense of it the only sensible reason any normal player stays out that long is if they get pinned in their zone and can’t change, surely the shots would overwhelmingly (and by that I mean 80+%) be in favor of the attacking team?
I suppose long-shift guys like Ovechkin are skewing that number upwards.
The small uptick for 0-6 seconds is from the attacking team’s defensemen jumping over the boards on an offensive rush.
Also, this statement is important in and of itself. Not a lot of people realize that certain defensemen get used in this manner all the time. The prototypical “underrated offensive defenseman” often finds himself being tapped on the shoulder when his team’s best forwards are moving the puck north.
Great post Gabe. I’m assuming all of these results are EV and that you somehow stripped that data. Any chance that you have the average EV shift length for every player? That would be interesting stuff.
Do you think this effect would be as pronounced on guys that take longer shifts in general. For instance, if the median shift for Player A is 40 seconds and for Player B it’s 55 seconds do you think Player B will be more effective from 50-55 seconds than Player A would be if he had a shift go that long? I tend to agree with RO that a lot of players are only taking these longer shifts when they’re getting caught. It would be interesting to see if these poor results persist for players who consistently take long shifts.
by Scott Reynolds on Feb 11, 2010 11:54 AM EST reply actions
1am? that’s usually when the good stuff starts.
by sunnymehta.com on Feb 11, 2010 11:58 AM EST reply actions
Alternative thought: maybe there’s just not enough data for the 100+ second shifts. The line just goes crazy there even though from 0 to ~80 seconds it is very smooth.
Good indicator that there’s a lot of noise in that area, maybe if we re-ran this ten years from now the 100+ second shifts would show huge negative Corsi %’s.
Umm, forgive me if i missed something, but isn’t there a huge bias here?
The shifts that will be longer tend to be the ones which CANNOT GET OFF THE ICE (because they’re stuck in their own zone) and thus will always have more shots against than for.
Right?
Correct. Additionally, when shifts get to the super long range, they will often-times affect BOTH teams. A team trapped in their defensive zone may still be playing against offensive foes running an equal shift length.
It’s easier to switch out the offense on the power-play, which is not included in these stats for obvious reasons. This also explains some of that noise that RO mentioned.
Does that solve it?
I was thinking about this when I wrote my post and came to the same conclusion with respect to guys getting hemmed in screwing things up. I’m not sure that looking at long shifts only will solve the problem though – you’re still going to have a bunch of guys out there who got hemmed in.
Based on what I see, most guys are useless after 45 seconds or so. I mean, I strongly agree with the premise of this post. I’m just not sure how to go about proving it.
I don’t think we’ll separate whether taking a long shift put the puck in your end or if the puck going into your end forced you to take a long shift. Clearly when you’re tired, you play worse!
I was thinking you could look at the next event following a D-zone face-off to see if players are less effective late in a shift. e.g – faceoffs after an icing where one team is tired and the other is fresh. But then I think you also have to deal with whether there was a TV timeout.
I think we’ll get a pretty good idea of things once we separate the data into individual players with different median shift lengths. If, say, Ovechkin is always taking 55s shifts, we know it’s not because he’s always getting hemmed in. So how does he perform, in general, from 41s-55s? And how does that compare with 0s-40s. If we can gather, say, 100 players who have a median at 50s or more we can probably come to some pretty decent conclusions.
by Scott Reynolds on Feb 12, 2010 3:27 PM EST up reply actions
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