Why is it so hard to evaluate individual defensive play? At the individual level there’s only so much a player can do to influence play on their own Players have to act as a unit -> Results are heavily influenced by teammates Player matchups can be more varies -> More influence of opponents Defensive systems can have a large impact on results -> Hard to compare across teams Granular data doesn’t exist for defence For offence we know the shooter, who had the assist on goals Goalies are voodoo and hate statistical analysts

What types of passes/shots are we interested in at the individual level? Metric Sh% Why do we care? Skill(s) Measured Entry Assists Against/60 7.2% Zone entry work has shown how important the type of entry is Zone Entry Prevention, Gap Control, etc. OZ Center Lane SAA/60 13.9% Expect this to be a skill – how well players control the middle of the ice Forcing play to the outside Behind the Net SAA/60 11.7% Higher danger shots against – expect that defencemen should be able to influence this by winning battles down low Winning puck battles in corners, maintaining position Royal Road SAA/60 27.6% Very high shooting percentage – could be influenced by ability to remain structured defensively or prevent rush attempts Preventing cross-ice passes Point Shots/60 2.6% Relatively low danger shots – could be influenced by keeping players to the outside Covering the point, keeping play to the outside

Defencemen - What’s repeatable? Split-Half Correlations (Does data in one half predict data in the other?) Which metrics seem to be most repeatable? Metric Split-Half R^2 Shots Assists Against/60 0.54 Entry Assists Against/60 0.53 OZ Center Lane SAA/60 0.32 Behind the Net SAA/60 0.39 Royal Road SAA/60 0.01 Point Shots/60 0.17 Entry Assists Against/60 In line with Eric Tulsky’s findings OZ Center Lane SAA/60 D need to control middle of ice Behind the Net SAA/60 D need to control area behind net Players with >= 250 minutes in each half (N=48)

Defencemen – Are these skills related? Correlations Between Defensive Metrics A fair amount of correlation exists within defensive metrics Entry OZ Centre BTN 1 0.66 0.55 0.78 Behind-the-net and OZ Centre- Line Passes are most correlated Both measure play in D-Zone Correlation isn’t perfect There can still be players who excel at one area but not the others Useful for deployment within a team Players with >= 500 total minutes (N=51)

Example: Randomly Selected Defencemen Metric P.K. Subban Shea Weber TOI 338.6 352.1 Rate Stats Entry Assists Against/60 15.4 16.7 OZ Center Lane SAA/60 9.6 10.2 Behind the Net SAA/60 4.1 2.9 Relative Stats Entry Assists Against/60 Rel 3.0 2.1 OZ Center Lane SAA/60 Rel 1.0 Behind the Net SAA/60 Rel 0.4 0.5

Forwards - Do they even matter on D? Split-Half Correlations (Does data in one half predict data in the other?) Forwards appear to have less control over defensive results Metric Split-Half R^2 Shots Assists Against/60 0.36 Entry Assists Against/60 0.48 OZ Center Lane SAA/60 0.31 Behind the Net SAA/60 0.19 Royal Road SAA/60 0.04 Point Shots/60 0.20 Lower repeatability across each metric Biggest influence on Entry Assists Against/60 Unfortunately, you actually do need to backcheck Some impact on Center Lane Shots Players with >= 250 minutes in each half (N=47)

Example: Buffalo Sabres Forwards – 2015/16 Player Name GP TOI OZ Center Lane SAA/60 Entry Assists Against/60 O'REILLY, RYAN 18 275.8 11.1 15.0 GIRGENSONS, ZEMGUS 19 253.6 9.0 14.9 LARSSON, JOHAN 17 221.8 7.8 14.6 REINHART, SAM 252.3 9.8 14.3 MOULSON, MATT 20 208.5 9.5 13.5 EICHEL, JACK 299.3 7.2 13.0 GIONTA, BRIAN 265.0 6.3 12.9 MCGINN, JAMIE 22 252.1 6.4 KANE, EVANDER 16 251.8 8.8 11.9 Noted Two-Way Center Ryan O’Reilly had the most Entry Assists Against/60 Noted Defensive Liability Evander Kane had the fewest Entry Assists Against/60