Sunday, May 3, 2009

Point Shots and Possession

One thing I wanted to look at in my playoff shot chart data was which teams were allowing point shots through and which teams were restricting them. I figured this was mostly related to defensive coverage. After having looked at the numbers and thinking it through a little more, however, it seems that the percentage of shots that originate from the point might be more of an indicator of possession than of defensive coverage.

Shots from some locations on the ice are very discretionary, such as for example shots from outside the zone or from sharp angles. The defence is usually relatively indifferent to these shots, because they are very unlikely to go in, which is why you don't see guys going down to block slapshots from the red line.

It is common, however, for teams to pressure the points and have multiple players attempting to block shots. Point shots can go in because of screens or deflections, or lead to other good results like rebounds. Therefore, point shots tend to be less discretionary - the defencemen will take the shot if they can, hoping for a deflection or a rebound. Because the front of the net is usually crowded with players, some puck movement is usually required to set up a point shot that ends up on net, and as a result point shots often occur after some sustained play in the zone. This means that teams that struggle to establish offensive zone possession are likely to have fewer point shot attempts and therefore fewer point shots getting through to the net.

My definition of a point shot is a shot recorded in the ESPN Gamecast as originating from between the top of the circles and the blue line, in between the faceoff dots. Here are the percentage of point shots out of total shots faced by each starting goalie in the playoffs:

Thomas 9%, Price 24%
Varlamov 16%, Lundqvist 20%
Ward 23%, Brodeur 20%
Fleury 15%, Biron 20%

Hiller 18%, Nabokov 17%
Osgood 12%, S. Mason 18%
Luongo 19%, C. Mason 15%
Khabibulin 13%, Kiprusoff 17%

The starting goalie that faced a lower ratio of point shots won 5 out of the 8 series. In all of those series, the winning goalie had a percentage at least 4% lower than the losing goalie. The 3 goalies that won despite facing a higher point shot percentage were Ward, Hiller, and Luongo, who all were excellent in round 1.

Point shot percentage did not have a very high correlation with either expected goals (0.08) or total shots (0.17), however, which suggests that it is not a perfect indicator. It is likely that some teams block more point shots than others, and that some teams attempt more point shots than others, depending on their team strengths and style of play, which of course would affect the numbers. There are also playing to the score effects. At least so far, however, the numbers have been intriguing.

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