Corsi 101

What is Corsi? You keep hearing this random term being thrown around in tweets, podcasts, and on TV, yet you don’t quite know what it means. You’ve googled it, but now you’re even more confused. Luckily, I’m here to try and simplify things for you.

Welcome to Hockey Stats College. Our first class is Corsi 101 and the lesson begins now. For help with the lesson, I’ve created a hypothetical game between the Blackhawks and Blues to helps describe Corsi

CORSI 101

Corsi is simply a measure of shots by both teams when a certain player is on the ice. But what is a shot?

For the longest time, a shot was considered to be a shot on goal. This is how it is shown in most of the NHL coverage. The shot attempt by Duncan Keith that was blocked by David Backes isn’t considered a shot by most people, because it wasn’t a shot on goal. It instead was a shot attempt that was blocked before arriving to the net, and thus thought as meaningless to the hockey world. But that shot attempt wasn’t meaningless! It showed that Duncan Keith, and thus the Blackhawks, were controlling the puck.

So again, what is a shot?

In the world of Corsi and puck possession, a “SHOT” is considered to be either a shot on goal, a missed shot on goal, or a blocked shot attempt towards the opposition’s net. Some people refer to these terms as shot attempts and that’s what they are.

So if Duncan Keith fires a shot wide of the net and gets the puck back, fires a shot that is blocked by David Backes, gets the puck back, and fires a shot that is stopped by Jake Allen, then that is three shots that will be used to measure Corsi.

Corsi = Shots.

Shots = All Shot Attempts.

It’s time to move past a shot only being a shot if it’s a shot on goal. From now on, there are shots and then shots on goal.

Okay, now that we know what a shot is, let’s dive into what Corsi is.

Corsi is a measurement of all shot attempts for both teams used to determine what team and even what player has the puck more and thus good possession numbers.

So let’s say it’s the end of the first period and Duncan Keith has zero individual shot attempts and he has a Corsi of +3. Again Corsi is basically shot differential. “But wait, if Keith never shot the puck, how can he have a positive shot differential?”

Good question. You see, Corsi takes the shot attempt total of the Blackhawks and the Blues when a player is on the ice. So for example if Keith is on the ice and The Hawks have 6 shot attempts and the Blues have 3 shot attempts, then Keith has a Corsi (shot differential) of +3. Even though he individually hasn’t shot the puck, he still is helping the Blackhawks stay in possession of the puck and obtaining 3 more shot attempts than the Blues when he was on the ice.

So now we know that Corsi is a dumb term for shot differential. But what about Corsi For? What about Corsi%?

Corsi For (CF) = Shot attempts by your team when you are on the ice. In the above example, Duncan Keith has a Corsi For of 6.

Corsi Against (CA) = Shot attempts by your opponent when you are on the ice. Above, Duncan Keith has a CA of 3.

Corsi (C) = Corsi For minus Corsi Against (shots for minus shots against) For Keith, 6-3= 3 so he has a Corsi (shot differential) of + 3.

Corsi For % (CF%) = is basically a representation of shot differential. Keith was on the ice for 9 total shots. He had 6 shots for and 3 shots against. Represented as a percentage, that would be 6 (shots for) / 9 (shots total) = 66%. When Keith was on the ice, the Blackhawks were in possession of the puck 66% of the time.

Now let’s switch up the numbers. Let’s say Keith is on the ice for 4 Blackhawks shots and 6 Blues shots.

  • Duncan Keith
  • Corsi for = 4
  • Corsi against = 6
  • Corsi = -2
  • Corsi for% = 4/10 = 40% possession.

With possession percentage, 50% is going to be the average line. Players and teams want to be above 50% possession which means they are out shooting the opponent.

If you follow me on Twitter, you will find I don’t usually use the term Corsi. It’s confusing to people and it complicates things that don’t have to be complicated. That’s why I use the simple terms like shots for, shots against, shot differential, and possession percentage. These terms are much easier for the regular hockey fan to understand.

Notes:

Shots for (Corsi for) could also be referred to as shot generation as a higher number would mean a player is helping generate more shots.

Shots against (Corsi against) could also be referred to as shot suppression. If a player has a low “shots against” number, then they are good at preventing the opponent from taking shots.

Acronyms found online

  • Shots for (CF, SAT for)
  • Shots against (CA, SAT against)
  • Shot differential (C, CD, SAT)
  • Possession % (CF%, C%, SAT%)

So now you ask the question, why is puck possession so important?

Most NHL teams score near the same pace. Hypothetically, let’s say all teams scores 10 goals for every 100 shot attempts. That would be 1 goal every 10 shots. If the home team takes 30 shots, they will likely score 3 goals. If the away team takes 10 shots, they will likely score 1 goal resulting in a win for the home team.

Corsi is all about outshooting the opponent which means having the puck more than your opponent, having more chances to score a goal, and limiting the opponents chances to score a goal. The opponent can’t score if they don’t have the puck. So that’s why we use Corsi to determine which teams possess the puck the most and which players drive possession.

So whenever you see the term “Corsi” just replace it with the word shots and hopefully that will help you better comprehend a badly named stat.

Hopefully I was able to help you understand what Corsi finally means. If you have any questions, ask me on Twitter, or emails me at BlackhawksBreakdown@gmail.com

Most people learn the best visually, so here is a video that covers what Corsi is: