From Hockey Prospectus
A statistic originally invented by Jim Corsi, who was the goaltender coach for the Buffalo Sabres. Corsi is essentially a plus-minus statistic that measures shot attempts. A player receives a plus for any shot attempt (on net, missed, or blocked) that his team directs at the opponent's net, and a minus for any shot attempt against his own net. A proxy for possession.
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.
This week I wanted to take a look at the possession statistics for individual players. I wanted to see the trends over time for players, as well as their total Corsi for the season to date. In doing so, I ended up overlaying their Fenwick and sizing by goals for as a way to provide a bit more context and better understanding as to player's roles on the ice and the results they are achieving (or not achieving).
What does this all mean? Let's take a look at Jackman. Negative Corsi. So when Jackman is on the ice, the other team is shooting a lot more than the Blues are shooting. But take a look at the color of his circle. It is a light blue which relates to a positive Fenwick. So in other words, yes the other team is taking a lot of shots, but Sir Jaxx is blocking those shots. Pietrangelo and Jackman lead the Blues in blocked shots with 72 and 65 respectively. But take a look at the Goals For for Jackman (size of circle or hover over circle to get exact stat). Him, Pietrangelo, and Stewart lead the team in Goals For (27).
So I can understand why some might want to hate on Jackman if you are just taking a look at one aspect of his play. But the reality is he is blocking shots and making hockey plays that convert into goals at the other end of the ice.
The game-by-game chart at the bottom looks messy, but all you need to do is click on a player in the top chart and the trend line for the player will be highlighted. You can see the trend over time for the player, as well as the results of each game. The lines are colored to show you the cumulative total of the player's Corsi over time. Perron definitely had a downward trend in Corsi but the last few games he has been trending upward. The big dip about 2/3 of the way across the chart? That is the San Jose game on March, 12th. I think all the Blues ended up in the negative even though the Blues won 4-2.
It is trade deadline today, but I am waiting till next week to take a look at the Blues new acquisitions. Also, if you are interested in the most recent player usage chart for the Blues, go check out the interactive dataviz I made for Rob Vollman's Hockey Abstract site. There are multiple filters and various options for coloring and sizing the bubbles.
Thank you for reading! Let's go Blues!