Blues by the Numbers: It's all about possession.

Fenwick (from Hockey Prospectus)

Another possession metric, originally devised by Matt Fenwick of the Battle of Alberta blog. Fenwick follows the same concept as Corsi, but doesn't include blocked shots. Fenwick is considered to have better predictive value for future goal differential than Corsi. The removal of blocked shots is also valuable since blocked shots are a proven skill worthy of being separated.

Fenwick Close % (from The Puck Stops Here)

Close Fenwick is defined as the Fenwick number when the game is within one goal in the first or second period and tied in the third period and overtime. This number is usually reported as a percentage of Fenwick evens that a particular team gets. Thus an average team has a 50% close Fenwick.

A couple of weeks ago, Chris Boyle, who writes for Habs Eyes on the Prize, put together one of the best hockey related data viz I have seen in a while. He took a look at teams' Fenwick Close from past seasons and whether or not they got into the playoffs. His results showed that teams which had a Fenwick Close of greater than 50% had a 75% chance of making the playoffs. You should go check it out right now (don't worry the link will open in a new window and we'll still be here when you are done reading it): Why possession matters: A visual guide to Fenwick.

What did you think? Pretty good stuff huh?

So I was inspired by his efforts at visualizing Fenwick to do a league wide data viz that shows each team's Fenwick trend (as a 5 game moving average) and ranking/shading each team's trend line based on their Fenwick Close.

The design of this chart is to give you a big picture view of a team's Fenwick trend throughout the season. I use a 5 game moving average in order to smooth out the line. The Y axis is the same for every team so you can compare trends lines between teams. The line that runs horizontally across the center of each team's chart is 0. So positive trending Fenwick looks like a mountain, while negative trends look like valleys. With the coloring and ranking, (white shading is approximately 50%) you can see which teams are most and least likely to make it into the playoffs based on the results of Boyle's analysis.

Taking a look at the St. Louis Blues, they rank high in Fenwick Close and if you look closely you will see their trend line is mostly positive, with only a few slight dips into the negative. When you read about the St. Louis Blues being a puck possession team this is what they are talking about.

The Fenwick Close numbers for the viz came from Behind the Net. The Fenwick numbers that I used for the 5 game moving average require some explanation. I got the numbers from the game logs at Time On Ice (go here for an explanation of how to use Time On Ice). Here is where it got tricky. Time On Ice usually provides team level Corsi and Fenwick game-by-game. However, for whatever reason, I have been unable to access just the plain Corsi/Fenwick pages this season. So thanks to @DrivingPlay and @FearTheFin for talking through with me on Twitter the other day about how to solve this problem. I ended up using the Fenwick numbers for the goalies as a proxy for each team's Fenwick. Goalies are the only players that are on the ice all the time during 5-on-5 even strength play. In the case that more than one goalie played in a game I used the sum of both goalies' Fenwick for that game.

I don't think there is any one stat that rules them all. But taking a look at trends over time in combination with key statistics and other tools like player usage charts can help you develop a better understanding of how teams are performing. Ever since I started this weekly installment here at St. Louis Game Time I find more and more great hockey data visualizations and great analysis. I hope that you find this as interesting and informative as some of the other great work out there and thank you for reading!