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08-13-2012, 11:50 AM
Czech Your Math
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Originally Posted by Jason MacIsaac View Post
Players have minimal difference on on ice shooting percentage. On ice shooting % is plenty more luck then skill. Some even suggest it is all luck in the long run.

NJ's PDO was wasted in 2011 by the shooting %, which was top 10 by seasons end this season. NJ was very unlucky with ES sv% during the regular season but look what happened in the playoffs.
Even on a team level, PDO is not purely luck. Neither of the components, SV% and Sh%, are pure luck. Yes, in the shorter term, luck is going to be the primary factor. However, in the longer term, each component will trend towards an expected and/or historical avg. based in large part on the skill of the players.

The reason it appears to be "luck" to some in the longer term is that:

1) The difference between goalies' SV%s tend to be very small in the longer term. For instance, the top 30 goalies in GP last season had overall SV%s that ranged from 894 to 930. So there is only so much difference to be expected from this component. This is not the same as saying that the expected SV% is the league avg., because it is not so for each team and therefore for each player on that team.

2) The differences in Sh% for a group of players also will have relatively small differences in the longer term. A line of Alfie-Spezza-Heatley would not be expected to have the same Sh% as an energy line of grinders. This seems like simple common sense.

Since each component has a relatively small range, the sum of them will also have a relatively small range. This doesn't mean that each player (or line or group) and each team will be expected to trend toward the league average.

I see limited use for this metric, but it may easily be misapplied by those who don't understand that each player/team has a separate expected PDO and that future expected PDO should not be influenced by past PDO. If Vancouver has a PDO of 1002 after 5 games, I may expect their future PDO to actually go up in the future, not down to 1000 as the metric suggests. If Vancouver had a PDO of 997 after 5 games, that shouldn't change the expected future PDO.

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