Are blocked shots really valuable?

Cam Charron
March 31 2012 11:51AM

If you're going to quote blocked shots in analysis, make damn sure that you're looking at an overall percentage of shot attempts blocked rather than the raw number of blocked shots.

And even then, it still may not matter.

You may remember a short time ago when I looked to dig through a few of the NHL's real-time stats and found that blocked shots actually correlate negatively with winning. When you think about it a little more though, it does make sense. Teams that block a lot of shots are more likely to both:

A - Spend time in their own zone

and

B - By proxy, give up a lot of goals

This is one of the principle factors behind Corsi, a puck possession metric that counts the number of shot attempts directed at the opposing net minus the shot attempts directed at the defensive goal. Teams that have a high Corsi number are very likely to spend a lot of time in the offensive zone, and vice versa.

So why do many analysts continue to bring up blocked shots as an indication of defensive play? Well, I don't really have an answer for that. Our Pass it to Bulisian friend Daniel Wagner, and a fellow write at the Backhand Shelf, introduced me this year to "Blocked Shot Percentage".

Wagner:

Blocking a shot is not inherently negative. In general, if an opponent is shooting the puck and you have the opportunity to block the shot, you do so. At the same time, blocking a shot is not inherently positive. Preferably, you are the one shooting the puck rather than blocking it.

Wagner's piece was inspired by something written by Derek Zona, who divided a player's even strength blocks divided by even strength shot attempts against in an effort to find out who the best shot blocker on the Edmonton Oilers was in December.

While Ladislav Smid had blocked 51 shots compared to Andy Sutton's 27 at that point, it's worth noting that Smid was on the ice for 434 shot attempts against his own net, and Sutton just 204, allowing Smid to rack up his shot block totals.

But it's easy to find that data for players, but I wanted to see if it had any real world application, as in, does ESBS% correlate well with winning? The answer is "no, but it doesn't correlate with losing like blocked shot totals do." I enlisted the help of Josh Weissbock who stripped team data from timeonice.com for the last three seasons, giving me team numbers in goals, saved shots, missed shots and blocked shots for and against each team.

The r-squared value (0 implies no correlation, 1 implies perfect correlation) of blocked shots to point percentage was -.144. For ESBS% to point percentage, it was only -.032. Not necessarily a good thing, still, to block a high percentage of shots, but it's still better than looking at the raw data alone.

We can logically assume why blocking shots isn't necessarily a positive, but can we also speculate as to why blocking a high percentage of shots doesn't clearly predict good teams? The easy solution would be to look at NHL scorer bias, since different arenas will have different criteria on what a shot block is, but I'm looking a bit beyond that. 

If you check behindthenet.ca's shot block tables, you'll see that many of the players who lead the league in having their shot attempts blocked are defencemen. Defencemen not only score at much lower rates than forwards (I calculated 3.9% to 9.6% at this season, respectively) but they also shoot from further away, usually taking shots from the points.

Getting a shot through the first defender and blocked by a scrum in front can create all kinds of chaos and rebound chances, and those are the types of shot blocks that we mostly see.

Most of the shots turned away by skaters aren't generally opportunities that would have resulted in goals in the first place. Perhaps if we looked at away numbers only, we'd start to see a more favourable correlation between blocks and wins, but I still have yet to think of any reason why blocking lots of shots as opposed to simply not giving them up is a positive.

63811cbf517d2d685ea09e103488ea3a
Cam Charron is a BC hockey fan that writes about hockey on many different websites including this one.
Avatar
#1 Scott McKenzie
March 31 2012, 01:34PM
Trash it!
0
trashes
Props
0
props

I agree with all that, I think there's just something to be said about guys who are willing to do it (and have a knack for it) rather than always need to do it because they're always locked in their own end.

Avatar
#3 VBS6935
March 31 2012, 02:51PM
Trash it!
0
trashes
Props
0
props

“I still have yet to think of any reason why blocking lots of shots as opposed to simply not giving them up is a positive”

Your comment has been stated before:

http://www.arcticicehockey.com/2010/7/1/1548346/bryan-murray-wants-other-team-to ""It’s great to block shots," Murray said in reference to Volchenkov’s specialty, "but I would like the other team to block shots. And you do that by having the puck, helping your forwards get the attack going and by being creative, particularly from the (defence)."

How many hockey games have you watched where one team had no shots on goal and/or scoring chances? Are we ever likely to see such a disparity in teams that this would be a regular occurrence?

I would think that we are never likely to see teams that are so good that they never give up shots on goal attempts or scoring attempts. And in the situation where two such teams met, perhaps blocking one shot might keep you from being on the short end of a one to nothing score.

If blocking shots is such a worthless passtime, why is it even tracked, and why do some GMs/coaches/players/fans seem to value it?

Either the people who value it are deluded, or, blocked shots is a too general and variable stat to have any value the way its currently tracked, or, perhaps it is being used in the wrong way (eg, wrong situation, wrong outcome, etc) to try to measure its value?

A look at the variability is given here: http://www.inlouwetrust.com/2010/7/8/1559914/blocked-shots-the-new-jersey

Blocked shots:

1. may nullify a definite scoring chance...these types of blocked shots are just lumped in with the total of all shots blocked unfortunately

2. may avoid shots on goal (which won’t be counted as a scoring chance) which otherwise might go in directly or on a tip or deflection

3. might be more valuable in front of a goalie who has a lousy save percentage

4. might be more valuable in some situations than others (like when the other team is on the power play)

Esoteric value of blocked shots:

1. Its a way players can show they are contributing to the team

2. They occasionally allow for odd man rushes the other way (exciting for fans, may create a scoring chance, etc)

3. Players who can get their shot around other players on a consistent basis are looked on more favourably than those who can’t and who seem to constantly have their shots blocked (especially on the power play)

4. Players who block shots may be looked upon with more favor by fans than players who don’t.

5. Does the defending team gain possession of the puck after a blocked shot more often than the team who took the shot? I don’t know if anyone has ever looked at this.

6. Does shot blocking cause the other team to change the way they try to score, especially on the power play? Do coaches plan strategy around this stat?

7. Is shot blocking demoralizing to the other team in some way?

There was an article about how managers of fantasy hockey teams might take advantage of this stat: http://www.leftwinglock.com/content.php?131-Navigating-Home-Bias-in-the-Blocked-Shots-Category

It may be that it is too early in the statistical life of the blocked shot stat to pay much attention to it, and until there is some standard way of keeping track of “critical” blocked shots at every rink, it is a stat best dealt with skeptibility...unless you are in contract talks with your team :)

Comments are closed for this article.