Fenwick vs. Corsi in Hockey: What's the Difference?

Corsi and Fenwick are two of the most commonly referenced advanced stats in hockey. They’re closely related, often discussed together, and sometimes used interchangeably — but they’re not the same thing. Understanding the difference between Fenwick and Corsi helps you know when to use each one and why analysts sometimes prefer one over the other.

Quick Comparison: Corsi vs. Fenwick

The core difference is simple:

Corsi counts all shot attempts — shots on goal, missed shots, and blocked shots.

Fenwick counts all shot attempts except blocked shots — so only shots on goal and missed shots.

That one distinction — whether blocked shots are included — is what separates the two metrics. Everything else about how they’re calculated and reported is essentially identical.

Why Does Fenwick Exclude Blocked Shots?

The reasoning behind Fenwick’s exclusion of blocked shots comes down to what the stat is trying to measure.

Fenwick is named after Matt Fenwick, a hockey analytics blogger who argued that blocked shots introduce noise into shot attempt data. His rationale: a blocked shot might say more about the defending team’s shot-blocking strategy than it does about the shooting team’s offensive play. If a team faces a shot-blocking-heavy opponent, their Corsi Against could spike even if they’re not actually giving up dangerous chances.

By removing blocked shots from the equation, Fenwick attempts to provide a cleaner measure of unblocked shot generation — which some analysts believe is a purer reflection of offensive and defensive play.

Breaking Down the Numbers

Both metrics follow the same structure. Here’s how they compare side by side.

Corsi For (CF): Shots on goal + missed shots + blocked shots (by the opposing team) while a player is on the ice.

Fenwick For (FF): Shots on goal + missed shots while a player is on the ice. Blocked shots are excluded.

Corsi For Percentage (CF%): CF ÷ (CF + CA) × 100. A measure of your team’s share of total shot attempts.

Fenwick For Percentage (FF%): FF ÷ (FF + FA) × 100. A measure of your team’s share of unblocked shot attempts.

Relative versions (CF% Rel and FF% Rel) work the same way for both — they compare a player’s percentage to their team’s percentage when that player is off the ice.

In practice, CF% and FF% are highly correlated. For most players and teams, the two numbers track very closely together. The differences tend to be small, usually within a percentage point or two.

When to Use Corsi vs. Fenwick

For most everyday hockey analysis, it doesn’t matter much which one you use. The two metrics tell very similar stories, and neither has been definitively proven to be more predictive than the other across all contexts.

That said, there are situations where one may have a slight edge.

Corsi is more commonly used in the hockey analytics community simply because it’s been around longer and is more widely cited. Most public analytics sites default to Corsi in their player cards and team dashboards. If you want to compare your analysis with the broader conversation, Corsi is the standard.

Fenwick can be more useful when evaluating play against teams that are known for extreme shot-blocking tendencies. If a team is blocking 20+ shots a game, Fenwick strips out that noise and gives you a clearer picture of the actual shot generation on both sides.

Fenwick is also preferred by some analysts for evaluating goaltenders. Since blocked shots never reach the goalie, Fenwick For Against (FA) represents the shots that were actually heading toward the net. This can provide a cleaner basis for assessing the workload and quality of chances a goalie faces.

Fenwick Close — Fenwick calculated only when the game score is within one goal — was one of the earliest refined possession metrics and still has a loyal following. Filtering by close-game situations reduces the impact of score effects (trailing teams shoot more, leading teams shoot less), and combining that filter with Fenwick’s exclusion of blocked shots produces a metric that some analysts find particularly stable.

Do Blocked Shots Really Matter?

This is the central debate. Critics of Fenwick’s approach argue that blocked shots are still legitimate shot attempts and reflect real offensive intent. If your team is generating shot attempts that get blocked, it’s still evidence that you’re controlling the puck and creating opportunities. Excluding blocked shots removes real information.

Proponents of Fenwick counter that a blocked shot is a partially successful defensive play, and that including it inflates the shot attempt count in a way that doesn’t accurately represent puck possession or offensive threat.

Research on this question is mixed. Some studies suggest that Fenwick is marginally more predictive of future outcomes than Corsi, while others find no meaningful difference. The honest answer is that the gap between the two is small enough that neither choice is wrong.

Which One Should You Use?

If you’re new to hockey analytics, start with Corsi. It’s the default in most conversations, most data tools, and most published analysis. You’ll be speaking the same language as the broader community.

As you get more comfortable, layer in Fenwick when the context calls for it — particularly when shot-blocking tendencies or goaltender evaluation are in play.

The most important thing is to understand what both metrics measure and what they don’t. Neither Corsi nor Fenwick accounts for shot quality. A shot from the slot and a shot from the point are treated equally. For that layer of analysis, you’ll want to explore expected goals (xG), which assigns a probability of scoring to each shot based on location, type, and other factors.

The Bottom Line

Corsi and Fenwick are more alike than they are different. Corsi includes blocked shots; Fenwick doesn’t. Both measure shot attempt differential as a proxy for possession, and both are reliable indicators of team and player performance. Use Corsi as your default, reach for Fenwick when context demands it, and pair either one with expected goals for the most complete picture.

---

Still building your analytics foundation? Read our full guides on what Corsi is, expected goals explained simply, and what RAPM means in hockey.