A quick refresher on hockey’s new statistics: puck possession correlates more strongly with winning than do things like goals or shots; measuring possession in a fluid game like hockey is difficult; as a practical solution, Corsi and its less-inclusive sibling, Fenwick, are statistics that track certain, more easily measured events (all shots, including on-goal shots and missed shots, and, in Corsi’s case, blocked shots), thereby serving as proxies for possession and, therefore, indicators of team success. Once you get past the names (as the NHL is in the process of doing), the concept is simple.
One way to improve Corsi might be to make it more comprehensive. If Corsi approximates possession by counting certain indicia of possession, it stands to reason that a similar metric could better approximate possession by counting more indicia of possession. In looking for other things to add, and keeping in mind that the practical computational benefit of Corsi is that it is comprised of easily tallied events, pass attempts– including both completed and unsuccessful passes– would seem to meet both criteria. Pass attempts indicate possession the same way shot attempts, as broadly defined under Corsi, do, and they should be nearly as easy to count.
I can think of two potential reasons why it might not make sense to expand Corsi to include pass attempts: 1) it is significantly more difficult to identify and count pass attempts than the shot attempts already being tracked, and 2) adding pass attempts to a possession proxy metric like Corsi does not significantly increase the value of the metric.
While the first might be true, it also may make it easier to collect more events. For the limited purposes of a relatively simple metric like Corsi, there should be no need to code or label the component events compiled into the single Corsi output. Adding pass attempts would save trackers from having to decide whether to include or exclude an ambiguous shot-attemptish thing. As for the second, I attempted to address this with someone who has written on the general subject, but, likely due to my own ineptitude, the exchange resembled two ships passing in the night, which is a terrible and sufficient way to conclude this post.
Bouncing puck: Passing, not shooting, is the key to scoring on the ice and the hardcourt
More on passing data and the shot quality debate – Hockey Prospectus
There’s no such thing as advanced sports statistics