Monday, July 15, 2013

Using Fenwick, Defensive-zone risk/reward and scoring chances-against to help quantify defensive-play

Quantifying a player's defensive play is substantially more difficult than quantifying their offensive contributions. Quality of competition and zone-starts have a huge impact on a player's defensive-numbers; a subject I'll tackle in a later post.

Defensive success-rate is calculated by taking the number of successful defensive-events in the defensive-zone, and dividing them by the total number of defensive-events. Events used in this calculation include; puck-battles, loose-puck recoveries, blocked shots, and intercepted passes.

Fenwick per-minute played is the number of shots that are directed on a player's net while they are on the ice. The fact that I track blocked-shots as a successful defensive event, is the reason why I chose Fenwick over Corsi; Fenwick does not include blocked shots, while Corsi does.

Defensive success-rate in the defensive-zone relates well to the number of Fenwick events against a player is on the ice for per-minute of ice-time; particularly for forwards.

The three forwards with the lowest defensive success-rates, also gave up the most Fenwick events against per-minute of ice-time. Those players were Michael Ryder, Rene Bourque, and Alex Galchenyuk. Two of the three forwards with the highest defensive success-rates in the defensive-zone gave up the fewest Fenwick events against. Those two players were Max Pacioretty and Jeff Halpern. The exception was David Desharnais. It's important to note that only 23.3% of Desharnais' zone-starts took place in the defensive-zone; lowest among Montreal centres.

For defensemen, defensive-zone risk/reward relates well to the number of scoring chances-against a defenseman is directly involved in per-minute of ice-time. D-zone risk/reward tracks both possession and defensive-events. This, combined with the large amount of defensive-zone events for defensemen help the two metrics match well.

Defensive-zone risk/reward relates well for d-men, while defensive success-rate works well for wingers

It doesn't match up as well for forwards; Likely because of the different defensive-zone responsibilities of each positional player, as well as the low number of defensive-zone events most wingers engage in.

PK Subban produced the highest defensive-zone risk/reward rating, while also giving up the third-fewest scoring chances against per-minute played. Andrei Markov and Alexei Emelin gave up the most scoring chances against per-minute played, while producing the two lowest defensive-zone risk/reward ratings. Francis Bouillon is an interesting exception, as he produced both a low defensive-zone risk/reward while also being on the ice for the second-fewest scoring-chances against. Bouillon played substantial even-strength minutes with a Norris Trophy winner, and only 29.4% of his zone-starts occurred in the defensive-zone.

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