The Hockey Index is a project that aims to provide fans and hockey enthusiasts with data that they can use to better analyze and understand the game. One of these metrics, popularly known as the Corsi score, helps to determine how effective players and teams are at generating shot attempts (corsi) and how effectively they prevent their opponents from doing the same (defence corsi). Although there is some variance from one year to the next, as expected, the general pattern is quite constant. Thanks to a new feature in the Hockey Index database that makes these metrics available for the 2020 NHL season, we can now easily answer the question: What does Corsi mean in hockey?
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Understanding Corsi In Hockey
Before delving into the specifics of the metric, it’s important to understand what it means. The Corsi score is the outcome of a shot attempt differential. To generate this score, we first need to determine the total number of shots (counted in the traditional sense) that were taken during a given game. Only then can we compute the proportion of these shots that were on goal. With this in mind, let’s examine how to calculate the Corsi score for an individual player:
The Basics
The basics of the Corsi score are quite simple: it’s the sum of shot attempts (counted and uncounted) that a player creates, either by taking himself or by having the puck touch the net, with or without the goaltender actively playing in the net, during a given game. The goal is to have the majority of shot attempts (i.e., more than 50%) be registered as attempts on goal. For example, if a player has 15 shot attempts (counted and uncounted) during a game, and five of them are registered as goals, the Corsi score for that player would be 15 + 5 = 20. In this case, the player would have a Corsi score of 20% (or 20 out of 100). The lower the percentage, the better.
The Uncounted Shot Attempts
Although we’ve discussed how shot attempts are counted in the context of the Corsi score, it’s important to note that a shot isn’t always counted as part of that metric. This happens when the shot isn’t on goal, when the goaltender successfully defends the shot, when the shot is blocked by the goalie’s skates, or when the shot is blocked by a defender and the puck is recovered by the goaltender, who then attempts to keep the puck in the offensive zone. In this case, the shot isn’t registered as part of the overall shot attempt total, meaning that the player’s actual shot attempt total for the game may be less than what is reflected by the Corsi score. This is called the unregistered shot and can’t be counted as part of the player’s Corsi score. For example, if a player takes a slap shot towards the net and the goalie successfully kicks the puck away, the shot isn’t registered as part of the player’s attempt total and therefore doesn’t factor into the Corsi score. This is different from situations where the puck is directly hit by the player’s stick, as in the case of a shot blocked by the goalie’s skates or by another player. In those situations, the player’s stick is considered to be the primary factor contributing to the shot attempt.
The Role Of The Goaltender
In some cases, the role of the goaltender can be quite substantial in determining the outcome of a given game. To take an example, if a team is scoring early in the game and the defense doesn’t have enough time to set up its defenses before the puck is dropped for the next shift, the team’s offense will get a significant boost from the goaltender’s active participation in the game. In this case, the team’s objective is quite simple: they need the goaltender to make as many save attempts as possible to keep the puck out of the net. Since we’re talking about keeping the puck out of the net, the defense will be the one doing most of the work. However, the fact that the offense didn’t have much time to set up its attack means that they will also be relying on the goaltender to keep the puck out. It’s also important to note that when the puck is in the air, the goaltender has an objective as well: to get the puck out of the air and into the net. This is a much more difficult task and, as a result, the goaltender doesn’t always succeed in keeping the puck out of the air. When this happens, the offense will get a chance to react and retaliate by firing more shots at the goaltender, creating more opportunity to score. In general, the more shots that are on goal, the more chance there is for the team to score. In most cases, the team that is generating the most shot attempts wins the game.
Defining The Different Types Of Corsi
As mentioned earlier, there are various circumstances under which a shot isn’t counted towards a player’s Corsi score. To understand the differences, let’s examine a few examples.
When the goalie stands on the line, he is considered to be at risk of being “out-corsi”ed” if the puck is in the air when he stops the initial shot attempt, as he will have allowed the shot to reach the goal. In this case, the goaltender is considered to be defending and the initial shot is called the ‘powerplay shot’.
If the initial shot is blocked, but the follow-up shot is not, the puck is in the ‘clear’ and the second shot is called the ‘penalty shot’. In most cases, the defending goalie is not at risk of being out-corsi’d by the subsequent shot because the follow-up shot is considered to be a continuation of the original attack and the second shot can be registered as part of the overall attempt total. As a result, the penalty shot is often a valuable addition to a team’s arsenal.
When the defending goalie handles the puck behind the net, he is ‘out-corsi’d’ if either of the following situations occur:
- the initial shot is stopped and no follow-up shot is taken (no ‘behind-the-net’ attempts)
- the initial shot is stopped and a follow-up shot is taken (‘behind-the-net’ attempt)
- the initial shot is not stopped and a follow-up shot is taken (both ‘behind-the-net’ attempts)
- the initial shot is not stopped and no follow-up shot is taken (‘behind-the-net’ attempt)
In all cases, when the puck is in the air and behind the net, the goaltender is out-corsi’d if any of the above situations occur. This includes the case where the follow-up shot is blocked by the defense. In this situation, the original attack is considered to be successful because the goalie either gave up the puck or allowed the opponent to score. As such, the puck goes back to the attacking team, who then has the opportunity to score again. In most cases, this will result in a 2-0 or 3-0 score. In some cases, it can be a matter of inches when the puck is ‘out-corsi’d’ in this manner. This is why it’s so important for goalies to keep a tight grip on the puck when it’s in the air behind the net.
Now that we know the different types of situations in which a shot isn’t counted towards a player’s Corsi score, let’s examine what effect that has on the metric.
The Impact Of Uncounted Shots In Corsi
As mentioned earlier, a shot isn’t always counted as part of a player’s Corsi score. Sometimes, the shot is blocked and doesn’t make it to the net. In other cases, the puck is kept in the air too long and another team gets a chance to shoot at it. In general, these ‘uncounted shots’ have a significant impact on the game. To illustrate, let’s look at a few examples.
If the puck is in the air and blocked, but the goalkeeper is still able to stop the initial shot attempt, the shot will be unregistered and will not factor into the Corsi score. In most cases, this will cause the goalkeeper to lose a little bit of ground in terms of overall save percentage, as the blocked shot doesn’t get registered as part of his total. In fact, if the initial shot is stopped and the follow-up shot is not registered, the save percentage for that individual game will be quite a bit lower. However, because the blocked shot was still allowed to reach the goal, the overall impact on the game will be largely positive.