A rant on Corsi and defensive performance

Recently, I have gotten into several discussions on the best defensemen in the NHL. A common theme I have encountered is people complaining that my list of best defensemen is too offensive, and that guys like Ryan Suter who are better defensively should be rated higher.

Now I have a problem with this idea, and I hope to lay out my argument in this fan post. First, let me talk about Corsi, since it is one of our primary tools when measuring player performance.

What people I think often forget about Corsi is that it is both a defensive and offensive stat. Corsi is a measure of the shot attempt differential while a player is on the ice, and thus both shots attempts for and against are accounted for in Corsi.

So let's say you have an amazing defensive defensemen. He is easily the best defender in the NHL, and when the other team has the puck he is able to dominate by causing turnovers and preventing shots on goal. In essence, he is the perfect defensive defensemen. When the opponent gets the puck and skates towards the goal, they reach this super defensemen and lose the puck.

Now let's also say that this defensemen has no offensive skill whatsoever. He doesn't make good breakout passes, can't stickhandle, and can't shoot. In essence, he is useful offensively.

What would the corsi for% of this super defensemen be? It would be 100%. His team would get 100% of the shot attempts while he's on the ice.

Now he for sure is a detriment offensively, so bad in fact that his team is basically playing 4 on 5 when they have the puck, but he is so good defensively that the other team wouldn't even get off one shot attempt.

Let's create another made up player. This guy is an offensive stud. He's like Bobby orr and Wayne Gretzky combined on offense. However, when the other team has the puck he shows the defensive ability of a beer leaguer. In other words, he sucks on defense.

So this player dominates when his team has the puck, but once the other team gets the puck he is terrible.

So what will his Corsi For % be, well it sure as hell won't be 100% like our super defensive player, since our offensive stud is so bad defensive. In fact, it might even be pretty bad, since he's basically forcing his team into a 4 on 5 scenario when on defense.

So what's the point of this made-up scenario?

It's to illustrate that Corsi measures defensive performance. If a guy is so good defensively as everyone claims he is, then that will be reflected in his possession metrics. Similarly, a guy who is bad defensively will see his poor defensive play reflected in his Corsi.

So when someone claims that guys like Erik Karlsson or Kris Letang are bad defensively, I see two options.

1) Those two guys are truly bad at defense, but they are so good offensively that they make up for their defensive liabilities and still end up as two of the most valuable defensemen because of their offense ability.


2) Those two guys aren't that bad at defense, or else we would see it reflected in their possession metrics. People just underrate their defensive performance for some reason.

This whole debate goes back to a quote from Dave Tippet about thinking about defense differently.

"We had a player that was supposed to be a great, shut-down defenseman. He was supposedly the be-all, end-all of defensemen. But when you did a 10-game analysis of him, you found out he was defending all the time because he can’t move the puck.

"Then we had another guy, who supposedly couldn’t defend a lick. Well, he was defending only 20 percent of the time because he’s making good plays out of our end. He may not be the strongest defender, but he’s only doing it 20 percent of the time. So the equation works out better the other way. I ended up trading the other defenseman."

I agree with Tippet here. I'd rather have the guy who is a worse defender but defends way less than the supposed shut down defensemen who is defending all the time.

This item was written by a member of this community and is not necessarily endorsed by <em>Broad Street Hockey</em>.

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