Handicapping Hockey – Corsi and Fenwick

Data.  Statistics.  Ratios.  Mathematical equations.  Yes, they are important, and all are utilized when handicapping any sporting event.  In hockey, two statistics that are often used to dive deeper into the game are called Corsi and Fenwick.  In this article,  we will dive deeper to what exactly these statistics are, what they are used for and how they are calculated.

What is the Corsi Statistic?

So what is the Corsi statistic anyway?  Well, it basically is a control or possession statistic first developed by former Buffalo Sabres goaltending coach Jim Corsi.  It has progressed since first developed, as many things have, but it still remains a commonly used and important statistic.  Basically, Corsi is the plus or minus amount of shots aimed at the net while at even strength (5 on 5).  This includes shots blocked, shots that hit the post, shots that are wide, shots that are high, tipped shots, or whatever else.  Basically, if you take a shot at the net, it is considered a “Corsi For” regardless of what occurs after you do so.  Conversely, if the other team (at even strength) slaps a shot on your defending net, it is considered a “Corsi Against”.

To throw an example into the mix to try to explain myself better, let’s say the Boston Bruins played the Toronto Maple Leafs.  The Bruins had 20 shots on net, 2 more shots hit the post, 5 shots were wide or high (missed the net) and 9 shots were blocked.  The Corsi would be 20 + 2 + 5 + 9 or 36.

The Maple Leafs had 24 shots on net, 1 shot hit the post, 6 shots were wide or high (missed the net) and 6 shots were blocked.  Here the Corsi would be 24 + 1 + 6 +6 or 37.

So, given the scenario above, on the Bruins side we would say the “Corsi For” is 36.  The “Corsi Against” is 37.  Conversely, on the Maple Leafs side, the “Corsi For” would be 37 and the “Corsi Against” would be 36.

What is the Fenwick Statistic?

And what about the Fenwick?  Well, it is pretty much the same statistic except take out the blocked shots from the equation.  Why? Because blocking a shot is considered a skillful act.  So, in above example, the Bruins would have 20 shots on net, 2 more that hit the post, and 5 more shots were wide or high (we exclude the 9 blocks shots).  The Fenwick would then be 27.

On the Maple Leafs side, the equation would look like 24 (shots on net) + 1 (shot that hit the post) + 6 (shots wide or high) = a Fenwick of 31.  We would not include the 9 blocked shots.

So, the Bruins “Fenwick For” would be 27 and the “Fenwick Against” would be 31.  The Maple Leafs would have a “Fenwick For” of 31 and “Fenwick Against” of 27.

Corsi and Fenwick as a Percentage

Both the Corsi and Fenwick statistics are oftentimes used in a percentage format.  To do this with above scenario, we would throw the data into the following equations.

Corsi Percentage = (1^st Team’s Corsi / (1^st Team’s Corsi + 2^nd Team’s Corsi)) * 100

Or using above example, the Bruins “Corsi For” percentage would be (36 / (36 + 37)) * 100

(36 / 73) * 100

.4932 * 100 = 49.32%

And the Leafs “Corsi For” would simply be 100% less the Bruins “Corsi For”.  Or 100% – 49.32% = 50.68%.

To get the Corsi Against, simply flip them.  “Corsi Against” for the Bruins would be 59.58% and the Leafs “Corsi Against” would be 49.32%.

Fenwick Percentage = (1^st Team’s Fenwick / (1^st Team’s Fenwick + 2^nd Team’s Fenwick)) * 100

Or using above example, the Bruins “Fenwick For” percentage would be (27 / (27 + 31)) * 100

(27 / 58) * 100

.4655 * 100 = 46.55%

And the Leafs “Fenwick For” would simply be 100% less the Bruins “Fenwick For”.  Or 100% – 46.55% = 53.45%.

Corsi and Fenwick in a Plus/Minus Format

Sometimes you will see the Corsi and Fenwick statistics represented in a plus/minus format.  All this really means is that, using the above scenario once again, the Bruins had a -1 (total corsi for minus total corsi against) for the game and the Maple Leafs were a +1.  And the Fenwick would be -4 (total Fenwick For minus total Fenwick Against) for the Bruins and a +4 for the Maple Leafs.

Applying the Corsi and Fenwick Directly to Players

An individual player’s on-ice Corsi or Fenwick is intended to showcase the individual player’s contribution to his team’s control of the puck.  To calculate the individual Corsi and Fenwick simply compute both teams’ Corsi and Fenwick statistics (in same manner as mentioned above) when that particular player was on the ice.

So Why do Most Calculate the Corsi and Fenwick When Playing 5 on 5?

So why do we look at both Corsi and Fenwick statistics when at even strength?  Well, for one, because the majority of shots taken in the season are at even strength.  A second reason would be that a team is going to take more shots at net when on the power play rather than when they are a player down.  This would distort the number.  Lastly, for individual statistics, what if a player was a penalty killing specialist?  That player’s Corsi and Fenwick would be fairly distorted.  Obviously, the same can be said for a player who is consistently on the power play.

Corsi and Fenwick – In Handicapping

Using the either the Corsi or Fenwick statistic (or both) when handicapping a game probably makes some sense now.  Basically, the Corsi and Fenwick statistics are ways we can track puck possession.  The rationale is that a team has a better chance at winning if that team possesses the puck more and takes more shots than the other team.  Taking the plus or minus form of the statistic mentioned above, a positive number would indicate that a team spends more time in the opposition’s end and, vice-versa, a negative number would indicate a team that spends more time defending.

A Few Places to Find these Stats

So, where can one find these stats?  Obviously, you don’t need to watch every game with a pen and paper in hand jotting down every shot attempt for each player and team.  Others have already done that and reported on it.  There are a bunch of websites out there that keep these kind of statistics.  Hockey-Reference.com is one.  I use this line of websites often when evaluating baseball (baseball-reference.com) and other sports.  See my article on collecting historical data here.  IcyData is another website to find these type of advanced statistics.

In Conclusion

While Corsi and Fenwick statistics are not the be-all end-all of hockey handicapping, I do believe they make good sense.  Try to use them in a future backtesting strategy and see if they can help increase your overall winning percentage.

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