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DBD Hockey Metrics Primer and Scoring Chance Project Update

Hockey Metrics can be very confusing. I try to make sure to provide as many definitions as possible when I use these stats and new ways of evaluating hockey players, but sometimes keeping everything straight is difficult for everyone. One thing I've felt was necessary before the season started was to put together a stats glossary-type post as a go-to post for any questions that arise throughout the season. I will keep this updated throughout the season, and add new information as necessary. I plan to link it to just about anything I do that involves stats of any kind.

Also, I have an update. In one of my first posts for Defending Big D I described The Scoring Chance Project, which is the effort to bring to the public scoring chance information that individual teams have tracked for decades by having individual people track NHL games. As the season draws nearer details are being finalized, and I wanted to take some time to pass on some final details.

Follow the jump to pick up the last tidbit of news about the project, and to peruse the glossary.

I have a couple bits of news regarding The Scoring Chance Project to pass along before we get into the stats primer. As of right now there are 14 participants in the project which should give researchers a significant amount of data even if it's going to be incomplete. The other piece of news is that we will have another tool at our disposal to analyze the scoring chance data at a finer level. A spreadsheet has been made available which will allow me to look at line vs line matchups in each game. We will be able to get a closer look at the impact of in-game player deployment decisions which will hopefully allow us to understand more about how the 2011-12 Stars function.

The rest of this post is more or less going to be a quick go to glossary for Hockey Metrics. I will add stat definitions and basic ideas to this list as time goes on. There is no way that I will get everything added before this is published, but that's ok. If you want something else added, or have a question about something Hockey Metrics-related just email me. If I don't know the answer I will know someone who does.

My goal with this is to keep it up to date as new research comes out, and to include as many links as possible to as many different prime source material locations as possible. I just look at the data, critique it, and try to analyze it. People infinitely smarter than myself actually initiate the discussions, and I would like to make their work accessible to anyone who has an interest.

I would also like to point out that much like any scientific or quasi-scientific endeavor these ideas and metrics can and will develop. At one time the idea of gravity didn't exist. The speed of light is considered the speed limit of the universe, but scientists might have broken it recently. It is higly encouraged that, if you are so inclined, you should pursue your own work to try to further the discussion because there are still numerous questions.

Alphabetically ordered. Keep in mind that for most of the metrics the number itself isn't nearly as important as how it relates to everyone else. A .120 QualComp alone doesn't tell us much, but comparing that to a player with a -.3 QualComp does.

+/- : Plus minus is the number of goals scored when a player is on the ice minus the amount of goals given up. It is a very misleading stat that doesn't tell much about an individual player. The numerous problems with +/- include, but are not limited to: the quality of the team the player is on, the difficulty of the minutes a player plays, plays the player has absolutely nothing to do with, goalie play, and numerous others. I will rarely, if ever, quote a players' +/-, unless it has an interesting abnormality.

Context: Context is the concept we all learned in middle school english. To appreciate any bit of information in any form it is in the best interest of the person analyzing the information to consider other factors that influenced the data. In terms of hockey cosider a player with a good defensive reputation, but a poor plus minus. Does that mean the player is poor defensively, or might he be playing more difficult minutes that artificially make his plus minus look worse than another player? Some examples of context are Zone Starts, QualComp, QualTeam, and the man power situation.

Corsi: This is the number of shots directed towards the net when a given player or team is on the ice. Negative Corsi means you give up more attempted shots than shot attempts you generate. Attempted Shots Against (negative) plus Attempted Shots For (positive) equals Net Shots Attempted, which is a player's Corsi Number.

Corsi Rel QoC: Corsi Relative Quality of Competition is an adjustment to the Quality of Competition metric. Quality of Competition is based on +/- which is a flawed stat. Corsi Rel QoC is the exact same stat as Quality of Competition, but it is measured with Corsi Relative which is a more accurate representation of the value of the competition a given player is facing.

Corsi Rel QoT: This short hand notation is for Corsi Relative Quality of Teammates. It's the same idea as Corsi Rel QoC in that it takes Quality of Teammates, and uses Corsi Relative instead of +/- to determine the quality of teammates a player is playing with on average.

Corsi Relative: Corsi Relative (Corsi Rel) is the difference between an individual player's Corsi number when he is on the ice versus what the team does when the player is off the ice. A positive number means that when the player is on the ice the team generates more opportunities than it does when the player is off the ice.

Fenwick Number: A Fenwick Number is very similar to a Corsi Number, but it doesn't include blocked shots.

GVT: Goals Versus Threshold is a stat created to compare the production (in terms of goals) that a player produces compared to what a replacement level player would produce (4th liners/AHLers/street free agents). If you are familiar with baseball statistics and the concept of VORP then you know exactly what GVT is. Tom Awad, the creator of GVT, wrote a three piece series describing how he came to the forumla for GVT. You can find parts 1, 2, and 3 Here, Here, and Here

League Equivalencies: The fun of following prospects is trying to figure out who the next great players will be. Gabe at Behind The Net worked on this issue here. Gabe's work allows us to roughly translate what a player from another league would be expected to do in the NHL based on production in the other league. Obviously, this doesn't always hold true to form, but it's a good gauge for what we can expect.

OPCT: Offensive Zone Percentage is a stat that shows how many offensive zone faceoffs a player takes compared to defensive zone faceoffs. It is a good indicator of what a coach thinks about the defensive utility of a given player. Poor defensive players/primarily offensive players will have a high OPCT because the coach wants to keep them away from their own ner or put them in prime scoring opportunities. The inverse is also true.

OZQoC (OZ Coke) charts: OZQoc charts are a graphical representation of the level of difficulty of the ice time of a given player. They plot Offensive Zone Start percentage and Quality of Competition on an x.y plane. Some also incorporate Corsi Relative. Below is an example.


QualComp/QualTeam: QualComp and QualTeam are shorthand for Quality of Competition and Quality of Teammates. These metrics are based on +/-, and they attempt to estimate how difficult the matchups a given player has assigned to him are, and the quality of teammates he plays with on average.

Quality Starts: Quality starts were introduced in Hockey Prospectus 2011-12. They are an attempt to more fairly judge the caliber of play of a given goaltender on an average night since going by a win/loss record, much like a pitcher in baseball, is relatively useless. A quality start is awarded to a goalie when he either stops more than the league average percentage of shots (around a .912 save percentage), or allows two or less goals when he sees less than 20 shots during a start. When a goalie satisfies either condition his team has a 75% chance of winning.

Rating: Rating is a metric from Behind The Net that compares a given players +/- to his teams +/- when he isn't on the ice. The idea is to remove the +/- team quality problem by seeing if a player overperforms or underperforms the rest of his team on average.

Scoring Chance: We're all familiar with Scoring Chances, but the concept is relatively open-ended. For this project there will be a more concrete definition. A Scoring Chance will be awarded when the puck is directed towards the net from a dangerous scoring area. If a shot is taken on the border of the defined area, but doesn't lead to any significant scoring opportunity it will not be counted. Blocked shots will not be included, but missed shots will be. The nebulous-sounding "dangerous scoring area" is loosely defined as the area inside "home plate" in the image below:


UFO%: Ultimate Face off Percentage is a metric Timo Seppa published as part of Hockey Prospectus 2011-12. The goal is to determine if there is a particular face off skill by eliminating as many biased sources of information as possible. Even strength road face offs are considered for the number which leads to a smaller than ideal sample size, but enough of a sample size to see that face off percentages are definitely impacted by outside forces.

VUKOTA: VUKOTA is a projection system from Hockey Prospectus based on their GVT stat. The system, like Baseball Prospectus' PECOTA, is used to project the future performance of current NHLers based on the historical performance of the entire set of all NHL players to ever play the game. Hockey Prospectus releases VUKOTA data yearly. You can find it in Hockey Prospectus 2011-12, or by going to the website and purchasing access for five bucks.

Zone Starts: Zone Starts are a contextual clue used to evaluate what type of minutes a player is used for on ice. It is a tally of where a player begins a shift off of a face off. When a player is on the ice for a face off in the defensive zone he is credited with one defensive zone start, in the offensive zone he is credited with an offensive zone start, and in the neutral zone a player is credited with a neutral zone start. Players who start more often in the defensive zone.

Useful websites:

Hockey Prospectus

Behind The Net Stats Page - You can find most of the stats listed in the glossary here.

Behind The Net Blog Hockey Metrics 10 Part FAQ (now Arctic Ice Hockey)

Irreverent Oiler Fans/


Ice Hockey Metrics

****If there is anything you would like added to this email me or send me a tweet @JoshL1220 .