blocked shot

You can use numbers to prove pretty much anything.

The NHL publishes five types of RTSS, or “real-time scoring statistics”. These are “hits” “blocks” “missed shots” “giveaways” and “takeaways”. They produce a mountain of data and quite oftentimes, there’s so much numbers available that people are constantly adding and subtracting and dividing these numbers to paint a rational picture of why teams are succeeding as they are.

This tweet from Sault-Ste. Marie Greyhounds head coach Sheldon Keefe caught my eye:

I’ve never met Sheldon, but I have heard that he has “a real affinity for advanced stats”. I’ve seen the RTSS used so many different ways. I saw a blogger two years back mention if Detroit is such a good hockey team, why are they always ranked so low in takeaways and blocked shots? (Her conclusion was that the Red Wings were flawed, not the numbers) I’ve seen people credit Toronto being first in hits for why they’ve improved this season (side note: after 19 games this season, the Leafs have 22 points. After 19 games last season, the Leafs had 22 points). I’ve seen defencemen judged by their “giveaway:takeaway ratio”.

The most egregious over-analysis of these numbers was CBC during last playoffs who added blocked shots and hits together to form some sort of catch-all “grit” rating that had the Rangers ranked very high. PJ Stock alluded to both numbers in the pre-game show for the Leafs game against Ottawa on Saturday. (Don Cherry Saturday mentioned toughness as a reason the Leafs are improved by, again, zero points)

The problem with these numbers is that they lie and that they really mean the exact opposite of what you’d think they mean. In the real world, a “giveaway” is actually preferable to a “takeaway”. In the real world, “blocked shots” correlate so highly with losing you may as well just be counting goals against. In the real world, the importance of “hits” is imaginary.

Let’s start with the obvious problem of these RTSS. They’re counted differently across every building in the league. The NHL separates them by home and road, so what I did is look at a bunch of different numbers including four of the RTSS and compared a team’s ability at home to that same team’s ability on the road. Basically, if a team gives away the puck a lot at home, they should give it away a lot on the road, right?

An r-squared of 0 implies a correlation of zero. An r-squared of 1 implies perfect correlation. The numbers in this post use data from the last three full seasons:

Statistic Home/Road r-squared
Fenwick Close 0.623
Goals Against 0.358
Goal Differential 0.297
Goals 0.244
Wins 0.186
Points 0.177
Blocked Shots 0.157
Hits 0.116
Giveaways -0.001
Takeaways -0.001

Fenwick Close‘ is the most repeatable of all these numbers. A team’s Fenwick rate is the number of unblocked shots taken by a team at the opponent’s net divided by the total number of unblocked shots by both teams. “Close” refers to the state of the game at even strength where the score is tied, or there’s one goal separation between the two teams in the first and second periods.

Goals, goals against and goal differential are all statistically significant substantial to some degree. Giveaways and takeaways are defined so differently from building-to-building that it’s hardly even worth comparing the two. Hits is also quite low. The Maple Leafs lead the NHL last season with 1279 hits at home and Calgary was last with 672. The Leafs had 939 on the road, and the Flames had 931. It’s almost identical when you make the setting a little more neutral.

That’s the first problem with RTSS: looking at “total” numbers isn’t a reflection of a team’s ability in a certain category. You could learn some things if you only looked at road numbers, though. Which brings us to our second problem with RTSS:

Of the four RTSS categories used by broadcasters, just one of them is in any way predictive of a team’s record. While commentators will bring up the Rangers’ ability to block shots (4th in the NHL with 1338 last season) they’ll invariably never mention good teams who do poorly in that category who are also good. The Los Angeles Kings and New Jersey Devils, for instance, were 29th and 30th in the NHL in blocked shots last season. Three teams that missed the playoffs (and two lottery teams) in the NY Islanders, Minnesota and Montreal were 1-2-3 in the league.

I wanted to see which of the above statistics was closer linked to wins. I looked at only the “road” number to see if it could predict the number of points the same team earned at home. Again, an r-squared of 0 implies a correlation of zero. An r-squared of 1 implies perfect correlation:

Statistic Ability/Points r-squared
Fenwick Close 0.218
Wins 0.199
Goal Differential 0.196
Points 0.177
Goals 0.084
Giveaways -0.002
Takeaways -0.003
Hits -0.021
Blocked Shots -0.117
Goals Against -0.119

Fenwick Close on the road, an obscure statistic found off on some random corner of the Internet, is actually the most predictive of a team’s home record—more predictive than even road wins, road goal differential, or points earned on the road.

And that’s something Hockey Night in Canada will never mention, at least not with PJ Stock or Glenn Healy on the camera who constantly slam their fists talking about the importance of toughness. Teams that have the puck the most tend to the win the most games. All of the useful categories involve some way or another having control of the puck.

Look at the bottom of the chart. The correlation between road blocked shots or road goals against and home points is pretty high, only the correlation is negative. What that means is that the teams that give up the most goals and block the most shots are the ones who are losing games. I find this fascinating, that blocked shots can have such a negative affect on a team’s record.

Less fascinating because the correlations are very small, but also hilarious, is that teams that give the puck away more are slightly better off than teams that lead in “takeaways”. Again, look at what Keefe said above—if hits are indicative of a team not having the puck, so are takeaways. Giveaways are an indication that a team has had the puck at some point.

So what’s the point of all this? Don’t trust what the raw numbers say. I’ve gotten used to calling advanced stats “performance metrics” to make them sound less elitist. That’s in contrast to “production metrics” like goals and assists and wins and losses. Fenwick Close % is a repeatable talent for teams both home and away that correlates more with a team’s record than any available number on NHL.com including wins. It’s predictive of success, and that is why I use it so often.

The mainstream success of Moneyball, if anything, has convinced a large audience of sports fans that there’s value to be found in using statistics with arguments to make points. The problem is that leagues have so much information available that it takes people a long time to figure out what’s worthwhile and what isn’t. To the casual fan, who gets into an online skirmish or two every month and watches Hockey Night each week, blocked shots are fine. The problem is that the numbers used often by broadcasters like the CBC who preach toughness at every available opportunity is that they weave a frail fiction of the game, and all too often, the statements of the PJ Stocks of the world go un-checked, leading to half the population of the Greater Toronto Area walking around like zombies and talking about how important Frazer McLaren has been to the Leafs’ this season.

By the way, as of Sunday night, Toronto is first in blocked shots on the road and 30th in road Fenwick Close %. The Anaheim Ducks are 9th in blocked shots on the road and 27th in road Fenwick Close %. I’ll let you guys guess what happens next.

Comments (33)

  1. “The most egregious over-analysis of these numbers was CBC during last playoffs who added blocked shots and hits together to form some sort of catch-all “grit” rating that had the Rangers ranked very high. ”

    This reminds me of the Hockey News’ ludicrous “power forward” rankings in the late 90s – early 00s. They’d award forwards extra credit for taking penalties, because it showed toughness.

    I think it was the Hockey Compendum (an excellent, early-advanced-stats-analysis book that’s only harmed by the fact that it was written by unrepentant Sabres homers who refused to acknowledge that Dallas won the cup in 99) who pointed out that, based on power play conversion and fighting majors as a proportion of penalties, you should actually deduct about 0.1 goals for every penalty minute a player incurs. It’s the whole “TOUGHNESS IS GOOD!” vs. looking at numbers rationally problem.

    It’s going to be much, much tougher to eradicate this from hockey than it will be from other sports simply because the commentary is so ludicrously awful to begin with.

  2. I would like to propose a new advanced stat called the “Cherry Ratio” (name is a work in progress).

    The calculation is:
    (Hits + Blocked Shots + Takeaways + Faceoffs Won) / 1000

    You have to divide by 1000 otherwise the numbers just look silly.

    This stat should indicate how much grit and toughness a team has. If you crunch the numbers for last year you can see that the Rangers were the toughest team in the league (obviously) with 6.579, but Toronto was actually second with 6.432. This year however Toronto appears to have a decent lead with 1.547 over Philly (which is another tough team of course) with 1.516.

    So with these numbers I would expect Toronto in the finals this year.

    • This is an excellent comment.

      • You see, the larger the numbers, it indicates more games played. Therefore the “Cherry Ratio” for last season’s teams are of course larger than the current season which is in progress.

        Seasons with larger numbers can indicate either more games or grittier teams. Actually, let me propose a modification, this will be called the “Balanced Cherry Ratio”.

        The calculation is:
        (Hits + Blocked Shots + Takeaways + Faceoffs Won) / (Games Played * 10)

        The numbers change slightly, but this takes into account the number of games played as well. The “Cherry Balanced Ratio” indicates interesting information, the best CBR teams currently are:
        1. Colorado: 8.211765
        2. NYR: 8.152941
        3. Toronto: 8.142105

        Interestingly these CBR values indicate that teams are grittier this year than last year. Last year’s best teams are:
        1. NYR: 8.023171
        2. Toronto: 7.843902

        This indicates a significant increase in the CBR for Toronto, which as I surmised in my original post means that they are a better team this year.

        • crap… I mixed up my new stat acronym already. It should be BCR not CBR… unless CBR sounds better.

          • If you knew anything about advanced stats, you’d know they need a nonsensical name that credits the creator, so…congrats on creating our newest stat, SPROUT.

          • As stated in the article though, you still should only count the hits (and possible others) on the road.

            Otherwise a team’s SPROUT could be influenced by a homer stat-keeper and that would just be ridiculous.

          • Damn that’s a good point. Should a team’s SPROUT take home ice advantage into account since it affects opposing teams as well? Or should it be a road based stat? I wouldn’t want to capture the wrong effects in a SPROUT.

            Perhaps a team’s road-SPROUT vs home-SPROUT value (a team’s SPROUT-ratio) could give an indication of how much a team takes advantage of its ‘home ice advantage’.

          • BCR’s – Budget Control Report..

  3. “In the real world, the importance of “hits” is imaginary.”

    Because L.A. didn’t hit anyone last year.

    Or Boston the year before that.

    It would be more accurate to say that in the real world, the hit statistic is useless.

    —-

    Listen, if I’m the Boston Bruins (over the past few years, lets say), I know I can physically dominate most teams, in large part by hitting. Does this mean I hit more than other teams?

    Of course not. When I’m playing Columbus, I’m not going to waste my energy hitting when I know I’ve got 81 other games plus playoffs and I can easily win without hitting. I’ll save my hitting for the playoffs, or for key matchups when I want to send a message.

    Also, hitting in one game is different than hitting over 7 games (like in a playoff series). The latter wears the opponent down, and pays off later in the series.

    If I wear Columbus down tonight so they are tired for Detroit tomorrow, what’s the point?

    In other words, statistics (esp. about hitting) are not very useful in the general sense.

    • Agreed, I hope tbis article is trying to show that hittin statistics are useless, not hitting itself.

      I mrwn, youcan crunch all these stats asfar as you want, but at somepoint even the best possessionteam wll not have the puck and will need to do something. Soketimes that means hitting…

    • The “B” could also stand for something else…

    • Bang on. The litmus test for the Leafs will be do they make the playoffs. There’s no question they are playing a much more physical brand of hockey. Does anybody really need stats to know that? You donwin the Cup without a high level of physicality. Even the highly skilled Red Wing teams had their bangers.

  4. Is there a way to explain why blocked shots correlate so poorly to winning, but Fenwick (which takes blocked shots into account, unlike Corsi) does? The way I understand it was that Fenwick didn’t count blocked shots as ‘shot attempts’ because it’s a measurable skill. So if it’s part of why your possession number is good, why would blocked shots as a standalone become so detrimental? Why wouldn’t Corsi be a better measure if blocked shots aren’t as valuable as we’re led to believe?

  5. Cam, in examining blocked shots did you look only at 5v5 or all situations? I wonder if there is a stronger correlation between blocking shorthanded shots and winning. A team’s shooting percentage seems to increase (relative to ES) by about 5% on the powerplay and shots against on the penalty kill are less correlated with the shorthanded team’s own ability than they are to the fact that they’re playing a man (or two) down.

    In other words, the increase in SH shots against are influenced by factors beyond the shorthanded team’s ability.

    • I used the readily-available data on NHL.com, since that’s what broadcasters and writers use. Doubt many have scripts that scrape out only 5-on-5 data.

  6. It is better described by saying it is a micro vs macro issue. In the micro a hit and block shot are good and help you when. In the macro having a lot is indicative of bad trend of possession. Again having a lot of blocked shots means the other team is taking shots.

    Of course the problem is a lot commentators don’t get that they see the positive in the micro and apply that to that the macro

  7. To paraphrase George Carlin, imagine a person you know of average intelligence. Half the world is dumber than him.

    CBC is only playing to their audience.

    • yep, CBC–and every other hockey broadcast.

      Way to take the elitism out of advanced statistics but why not lay off the little guy?

  8. You’re the worst. Go back to Hastings & Main.

  9. can i get a white power?.. for the road team of course

  10. This is a great article.

    Since blocked shots is getting so much attention in the comments section, I figured I would add one thought I had about this particular skill / statistic.

    I totally agree with Cam’s assessment of the RTSS, and I think that accepting that these statistics are not predictive or indicative of team performance would be a huge step in the right direction for the hockey community. On the other hand, I find the RTSS interesting because even though a statistic (say blocked shots) is totally useless when trying to evaluate a team, no one is suggesting (or at least they shouldn’t be suggesting) that teams should get their players to stop blocking shots.

    When an opposing player is about to take a shot at your net, it’s better for you to step in front and try to block it than to let it go through on your net. A shot attempt against is much preferable to a shot on net against. The fact that the other team was shooting toward your net in the first place is an indication that they had the puck, and since puck possession is a key predictor of wins, it would have been better if they’d not had the puck in the first place.

    The same would be true for a stat like takeaways. Cam has shown that takeaways are useless in assessing team performance, but if the opposing player has the puck the “analytical damage” (so to speak) has been done. Your player should obviously still try to take it away.

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