Why Scoring Chances Are Important

Alex Ovechkin shooting

Photo credit: Thearon W. Henderson

They talk about them on the pre-game shows. Coaches lament about how many or how little they had. I write about them. They’re everywhere. Scoring chances are a new craze sweeping North America. By my count seven teams are currently being tracked, the Oilers by Dennis King at MC79hockey.com, the Flames by Kent Wilson at Flames Nation, the Rangers by George Ays at Blueshirt Banter, the Panthers by Derek Zona at Litter Box Cats, the Canadiens by Olivier at En attendant les Nordiques, the Leafs at Under the Helmet of Slava Duris and the Caps by yours truly. Find out why after the jump.

So we are all on the same page, let’s first define what I mean by a “scoring chance:”

A scoring chance is defined as a clear play directed toward the opposing net from a dangerous scoring area – loosely defined as the top of the circle in and inside the faceoff dots, though sometimes slightly more generous than that depending on the amount of immediately-preceding puck movement or screens in front of the net. Blocked shots are generally not included, but missed shots are. A player is awarded a scoring chance anytime he is on the ice and someone from either team has a chance to score. He is awarded a “chance for” if someone on his team has a chance to score and a “chance against” if the opposing team has a chance to score.

For those of you that want something more visual, take a look at the diagram below. Shots from the green area are where I log scoring chances. I am going to further divide the rink so we can see just how more effective shots from the chance area are versus the rest of the ice. The light blue areas represent just outside of the scoring chance area, but still within the top of the circles. The darker blue areas extend from the top of the circles to the blue line and the purple area extends that further back to the red line (center ice).

NHL rink with areasI took location data for shots on goal and goals scored during even strength from 100 random NHL games that have been played this season, and then plotted them on the rink. Blue circle indicates a shot on goal, green circle a goal scored.

EV shots from 100 random NHL games 2010-11 rmnb

Here is the shot data by section:

Location Goals Shots Sh%
blue line to red line (purple) 2 152 1.30%
blue line to top of circles (blue) 89 2049 4.16%
left/right scoring area (light blue) 16 240 6.25%
Scoring Area (green) 411 2487 14.18%

Far and away the best shots are those taken in the scoring chance area – more than double the next best position on the ice. Through 61 games, Washington has converted on 14.1% of their scoring chances, which appears to be close to league average.

Now you see why I pour over scoring chance data: it’s where the action is. A team’s ability to get scoring chances will impact its ability to win games. More chances = more goals = more wins. Another stat that is correlated to wins is Corsi, which measures the net difference between shots directed at the opposition’s goalie, including those missed or blocked. The higher the number, the better that player is at driving puck possession. Corsi is great, but I think scoring chances give a better idea of individual contribution. For example, suppose you have two players, each playing with similar quality of linemates (Corsi QoT), getting a similar number of offensive zone starts (OZone%) but generating very different Corsi numbers.

Name Corsi/60 Corsi QoT Ozone%
Player A 11.14 3.08 54.6
Player B 6.39 2.88 53.0

I think most would agree ‘Player A’ looks like the better bet. More net shots directed at the opposition’s goalie means greater puck possession. However, when we look at net 5v5 scoring chances per 60 minutes, we see a different picture.

Name Corsi/60 CORSI QoT Ozone% SC/60
Player A 11.14 3.08 54.6 2.63
Player B 6.39 2.88 53.0 2.96

‘Player B,’ despite being on the ice for less net shots directed at net, has been on the ice for more net scoring chances per 60 minutes and also sees a much higher percentage of shots as scoring chances. Remember, more chances mean more goals, which means more wins. Incidentally, ‘Player A’ is Mathieu Perreault and ‘Player B’ is Brooks Laich from this season.

So you see, we bloggers are clearly on to something — and it’s the same thing that NHL teams have tracked for some time.

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  • Colin

    Thanks for the post Neil. I have a question about shots from outside the high quality area that lead to juicy rebounds inside the high chance area. I would imagine a good number of the high quality chances and probably an even higher percentage of the high-quality goals came following a nice rebound off a shot from a lower quality area. Is this somehow tracked or quantified? I think especially for centers and D-men, this would be an important indicator of worth regarding team offense.

    Thanks again for the post Neil. PS, anyone you think we could pick up at the deadline that has a good SC/60?

  • PainKiller

    Because a scoring chance is, to some extent, subjective I’d like to know if there there would be a statistically significant difference in results if two or more independent charts were assembled.

    It seems to me that there is room, though I don’t know how much, for numbers to differ. 1) “loosely defined as the top of the circle in and inside the faceoff dots,” 2) sometimes slightly more generous than that depending on the amount of “immediately-preceding puck movement or screens in front of the net,” 3) “Blocked shots are GENERALLY not included,” (Emphasis added.)

    What about tip ins, or missed tip ins? What about a screened goalie? One can argue that what looks like a screened goalie might actually not be screened or vice versa, Depending on the screen a shot might result in a high quality scoring chance. Define a blocked shot? A non-goalie can block a shot in the crease. Does that count a scoring chance?

    Probably a situation of this being a stat that is just “better than what was used.” But with so many variables and perspectives, I come back to my original question. How would independent reports look?

    Thanks so much for everything you do. Love how you make me think about the game. Fantastic!

  • http://www.russianmachineneverbreaks.com Russian Machine Never Breaks

    @PainKiller you bring up some good points, but I think I can boil it down to this:

    We try to be as consistent as we can. George and I had almost identical counts for the WSH – NYR game, and with only 7 teams (we know of) being tracked by bloggers we don’t get the benefit of comparing notes as often as we like.

    As for the chart above, those are just shots on goal recorded by the NHL, there is no “interpretation” of the stat. The only interpretation is by me sectioning off areas of the ice.

    Thanks for reading!

    -N

  • JWare

    Neil, what does having a -6.76 corsi mean? I’m assuming its bad…?

  • http://www.russianmachineneverbreaks.com Russian Machine Never Breaks

    @JWare Corsi is the shot differential while a player was on the ice. This includes not just goals and shots on goal, but also missed and blocked shots — the differential in the total number of shots directed at the net. So a -6.76 Corsi means that for every 60 minutes that player is on the ice, the team will see ~7 more shots (incl goals, saved, missed and blocked) directed at their net. In essence, less time in the attacking zone and more playing defensively.

    Now, if you’re asking specifically about MJ90, the number is actually WORSE than it looks, because he starts so often in offensive zone (~59%). But he is also a rookie, so that needs to be factored in as well.

  • PainKiller

    No, Neil, thanks for replying. I hope that over the course of time we will see others track this statistic and look at how interpreting a scoring chance has any significant affect on the bottom line.

    I recall the quote “The best is the enemy of good.” (http://www.famous-quotes.net/Quote.aspx?The_perfect_is_the_enemy_of_the_good) I’ll shut up now. :-)

    All the best,

  • Mike

    “Scoring Chances” was invented by EA Sports so that people who sucked at NHL ’95 could feel good about themselves. “I lost 7-0, lost 5 fights, had 3 shots on goal, but I had 7 scoring chances! Whoo hoo!”

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