Corsi vs Fenwick
Understanding shot attempt differentials and possession proxies in the NHL.
Ice hockey is a fluid, low-scoring game. Because goals are rare and heavily influenced by goaltender variance and luck, analysts needed a proxy for puck possession. Enter Corsi and Fenwick.
Corsi (Shot Attempts)
Named after goaltender coach Jim Corsi (though popularized by blogger Tim Tull), Corsi is simply a plus-minus metric for all shot attempts. A team controlling the puck will naturally direct more attempts toward the opponent's net.
Corsi For (CF) = Goals + Saves + Missed Shots + Blocked Shots
Corsi Against (CA) = Opponent's Goals + Saves + Missed Shots + Blocked Shots
Corsi For % (CF%) = CF / (CF + CA)
Fenwick (Unblocked Shot Attempts)
Named after Matt Fenwick, this metric is identical to Corsi, with one critical difference: it removes blocked shots from the equation.
Fenwick For (FF) = Goals + Saves + Missed Shots
Which is better? A Worked Example
Imagine Team A generates 20 attempts, but Team B's defense aggressively blocks 10 of them. Team A's CF is 20, but their FF is 10. Does a blocked shot represent a successful offensive possession or a successful defensive stand?
Historically, Corsi has a slightly higher correlation with future goal-scoring (possession volume matters most). However, Fenwick has a higher correlation with current scoring, as unblocked shots are inherently higher quality. Analysts today use both, but often default to Corsi for evaluating long-term possession dominance.
Common Mistakes
- Ignoring Score Effects: Teams trailing by multiple goals will almost always generate higher Corsi numbers as the winning team plays a conservative "shell" defense. Always adjust for score and situation (5v5 Score Adjusted).
FAQ
- What is a good CF%?
- Any CF% over 50% means you control the majority of play. Elite teams consistently sit in the 53-55% range over a full 82-game season.