Posted by: kristagolden | March 31, 2014

## Fancy Stats: A Crash Course in Basic Corsi and Fenwick

We’re all familiar with the basic hockey stats: points, goals, plus/minus, faceoff percentage and the like. But lately, all you hear about is Corsi and Fenwick in terms of statistics. These new ones make some people’s head spin while others simply ignore them, but they’re important because it tracks a team’s (or a player’s) puck possession – basically, more possession is a good thing because that leads to goals. This is as close as you can get to actually timing a player or team when they have the puck.

With the help of articles from Fear the Fin and my friend Jen (the Marchioness of Hockey Metrics) at Second City Hockey, I’ll try to break this down. Bear with me because it involves math, which makes many people cry.

Here are the basics:

Shots on goal + missed shots + blocked shots = Corsi number

Shots on goal + missed shots = Fenwick number

To go along with that, there’s Corsi For (Fenwick For) and Corsi Against (Fenwick Against). Corsi/Fenwick For is the all the shots taken by a particular team in their games, whicle Corsi/Fenwick Against is all the shots made at their net. Because Corsi uses blocked shots, it’s seen as a short-term stat, while Fenwick is a long-term stat. It’s kinda like 3-day and 10-day weather predictions, only a bit more accurate.

Let’s use the top team in the league right now, the Boston Bruins, to illustrate Corsi and Fenwick (with numbers courtesy of extraskater.com).

Through 75 games, the Bruins’ Corsi For (CF) is 3548, while their Corsi Against (CA) is 3061. This means that they’ve made 3548 shots in their opponents’ nets while the other guys have made 3061 in theirs. If you subtract the CA from their CF, they have a +487 Corsi. To convert that into a percentage:

3548 + 3061 = 6609

3548/6609 = 53.7% CF

That’s not bad, as it has them fifth in the league (the top team is the Los Angeles Kings). Their Fenwick is just as good: 2632 FF and 2304 FA for a +328 Fenwick. For that percentage:

2632 + 2304 = 4936

2632/4936 = 53.3% FF

Also fifth in the league (the Kings are tops in Fenwick as well). Not bad at all.

Corsi and Fenwick can also be used to track possession for players. In this case, the CF/FF is all the shots a player’s team makes when he’s on the ice, while CA/FA is all the shots the other team makes when he’s out there. Since we’ve used the Bruins for the team example, let’s go with Patrice Bergeron and his possession game. You do the same calculations as you would for the team.

Patrice’s CF is 1092, while his CA is 698. That’s a +394 Corsi, or an even 61% CF.

His FF is 814, and his FA is 533 for a +281 Fenwick or 60.4% FF. That’s good for first in the league in both.

There are other stats you can check, such as a player’s Corsi/Fenwick For compared to his team’s CF/FF when he’s not on the ice. A quick look at Extra Skater can help you dive into other situations like penalty kill and power play, but to really track a player or team over time, even strength (5v5) is best.

And here are three terms I’ve heard a lot: Score Effects, PDO and Close:

Score Effects – When a team has a lead, it usually goes into defensive mode, which makes the team that’s losing go on the offensive and shoot more. This gets more intense if you’re nearing the end of the game.

PDO – this is basically a player’s shot percentage + save percentage (how many of his shots have been saved)

Close – a Score Close is any scored that’s tied, including a scoreless tie, or within one goal. Once you get to the third period, only ties count.

There’s your dip into the land of Advanced Hockey Statistics. If you have questions, you should follow Jen (a fellow Blackhawks fan, but she’s cool) on Twitter. She tweets team numbers a lot and is good folks in general. And her Twitter handle is pretty awesome.