Can Teams Win By Taking Higher Quality Shots?

Jonathan Willis
November 09 2011 11:05PM

Shot quality is a hot-button issue among people who spend time trying to learn about the game of hockey through statistical analysis.

Intuitively, we all know that shot quality exists. A quick blast from center ice immediately prior to a line change is far less likely to score than a superstar taking a shot on a breakaway. The question, then, isn’t whether shot quality exists – we know it does – but whether teams can use it to help them win games.

Defensive shot quality is hard to measure because of goaltending effects. If Boston posts a better save percentage this season than Columbus, we can’t say that it’s strictly a matter of their team playing better defense or a brilliant coaching stratagem – because Tim Thomas and Steve Mason are very different goaltenders. Various methods of measuring shot location to split defensive performance from goaltending performance remain problematic and unproven.

That problem, however, doesn’t exist when we look at team offense. A team’s shooting percentage tells us exactly how likely they were to score on any given shot. Therefore, if certain teams in the league are better than others at taking quality shots, it’s something that should show up when we look at their records from year-to-year.

Naturally, we’d want to level the playing field – some teams get more power plays or penalty kills, some teams spend more time in 4-on-4 situations, etc. To get a really even idea of what teams are good at taking quality shots, we’d only want to look at 5-on-5 game play – it’s the most common situation, the area where coaching and overall team ability should be most evident.

If we go back to 2010-11, the best team in the league at converting their shots was the Philadelphia Flyers. In 2009-10… they were the 27th-best team in the league. The Capitals were the best team in the league in 2009-10, and they fell all the way to 23rd in 2010-11. In fact, the average finish of a team that leads the league in shooting percentage in the previous and prior years is 14th overall in the NHL. Interestingly, the average finish of a team that finishes last in the league in shooting percentage in the previous and prior years is also 14th overall.

Still, those are just examples. To really see if shot quality matters offensively, we’d want to look at the entire league, over a period of years. Thanks to Behind the Net, we can do that – we have four years of 5-on-5 shooting data, from 2007-08 to 2010-11. We’ll run mathematical correlations, to see the relationship from one year to the next – a score of 1 represents a perfect correlation, a score of zero shows no correlation whatsoever.

  • 2007-08 to 2008-09 correlation: 0.179
  • 2008-09 to 2009-10 correlation: -0.067
  • 2009-10 to 2010-11 correlation: -0.121
  • Average year-to-year correlation: -0.003

The average correlation is actually slightly negative over these years, but it’s very, very close to exactly zero. In other words, there seems to be no connection between how good a team’s shooting percentage is from one year to the next. This is a significant argument that there is no major difference between individual NHL teams in their ability to score on any given shot – over the big picture, shot quality in 5-on-5 situations evens out.

While a team’s shot quality seems to bounce around erratically from year to year, the same is not true of the number of shots that they take. Here are the same correlations, but this time instead of looking at team shooting percentage, we will look at team shooting rates (shots/60) in 5-on-5 situations:

  • 2007-08 to 2008-09 correlation: 0.578
  • 2008-09 to 2009-10 correlation: 0.453
  • 2009-10 to 2010-11 correlation: 0.462
  • Average year-to-year correlation: 0.498

That’s not a perfect correlation by any means, but there’s clearly a relationship between how teams perform from one year to the next – something we didn’t find when we looked at shot quality.

Because shot rates are at least somewhat predictable, we can view them as a team skill – teams that are good at this one year stand a good chance at being good at it the next year. Because shooting percentage is unpredictable (at the team level) it becomes very difficult to argue that certain teams are better at it than others.

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Jonathan Willis is a freelance writer. He currently works for Oilers Nation, Sportsnet, the Edmonton Journal and Bleacher Report. He's co-written three books and worked for myriad websites, including Grantland, ESPN, The Score, and Hockey Prospectus. He was previously the founder and managing editor of Copper & Blue.
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#51 Romulus' Apotheosis
November 10 2011, 10:45AM
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Robin Brownlee wrote:

:book¡e: You will have to wait until I finish figuring out how to make my Betamax deck stop flashing "12:00."

But clearly us aficionados know that Beta is a far superior system to VHS. No matter what those VHS troglodytes say about performance, efficacy and ubiquity we have the specs on our side! Long live Beta, the machine of technological erudition!!

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#52 Romulus' Apotheosis
November 10 2011, 10:51AM
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looks like Renney is not done sweating MP:

http://www.630ched.com/Channels/Reg/OilersHeadlines/Story.aspx?ID=1569508

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#53 OB1 Team Yakopov - F.S.T.N.F
November 10 2011, 10:51AM
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Just so I'm clear here, this is saying that shot quality doesn't really matter? ... ie over a large enough sample teams are going to score at roughly the same rate?

ie if you consitantly out shoot, you should consistantly win?

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#54 ubermiguel
November 10 2011, 10:53AM
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Robin Brownlee wrote:

Bruce McCurdy with a long look at outshooting and wins etc at The Journal from last July: http://blogs.edmontonjournal.com/2011/07/18/paradigm-shift-the-evolving-relationship-between-outshooting-and-winning/

@ RB; Cool read, thanks. Good luck with the Betamax.

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#55 Quicksilver ballet
November 10 2011, 11:20AM
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No!

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#56 Slats
November 10 2011, 11:45AM
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@Dave Lumley

That's profound and funny.

I guess that's why the saying is "He shoots, he scores"* and it's not "He selects, he thinks, he overpasses, he scores"

*exception is Ryan Smyth "he passes/shoots off dman's butt/stick/shinpad, he scores"

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#57 Clyde Frog
November 10 2011, 02:49PM
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Willis, I appreciate what you try to do with adding statistics to Hockey, but you really need to post your Descriptive Statistics and regression tests on known years to demonstrate causation along with correlation.

Have you stat buffs been doing that stuff for all the popular measures?

Please don't take this post as a jump down anyones throat, just trying to understand what is going on behind the claims.

I understand how baseball statistical analysis works, but thats because you can break down 95% of interactions into a single interaction between player and measurement. Hockey is a much tougher bird to look at because there are 9 other players on the ice, different systems, 2 referees and a whole host of other factors that go into a single play. (Outside of shootout attempts)

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#58 Semenko and Troy
November 11 2011, 08:18AM
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Sit Barker. He moves at the speed of glacial ice.

Sit Gagner. Opt for more size and speed through the line-up. RNH-Hall-Eberle

Horcoff-Smyth-Jones

Lander-PRV-Hemsky

Belanger-Eager-Petrell

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