Monday, June 11, 2007

Vezina Trophy: Goal Games

Since shutouts are worthless to evaluate goalies (link), let's look at the frequency of all goal-games for Luongo and Brodeur.

Here are the breakdowns, taken from an HFBoards thread:

0 goals: Luongo 5, Brodeur 12
1 goal: Luongo 20, Brodeur 15
2 goals: Luongo 19, Brodeur 19
3 goals: Luongo 20, Brodeur 18
4 goals: Luongo 8, Brodeur 8
5 goals: Luongo 3, Brodeur 4
6+ goals: Luongo 1, Brodeur 2

These types of charts aren't seen too often, so we need to introduce some context and make sure we are making fair comparisons. I used a binomial calculator (http://faculty.vassar.edu/lowry/binomialX.html) to calculate the expected number of shutouts, one-goal games, etc., for both goalies, as well as for an average goalie, based on save percentage and average number of shots faced.

Brodeur:

0 goals: 8.0 expected, 3.7 average, 12 actual, +4.0
1 goal: 19.0 expected, 11.8 average, 15 actual, -4.0
2 goals: 21.7 expected, 18.3 average, 19 actual, -2.7
3 goals: 15.9 expected, 18.4 average, 18 actual, +2.1
4 goals: 8.4 expected, 13.3 average, 8 actual, -0.4
5 goals: 3.4 expected, 7.4 average, 4 actual, +0.6
6+ goals: 1.5 expected, 5.1 average, 2 actual, +0.5

Luongo:

0 goals: 7.0 expected, 3.6 average, 5 actual, -2.0
1 goal: 17.4 expected, 11.5 average, 20 actual, +2.6
2 goals: 20.0 expected, 17.9 average, 19 actual, -1.9
3 goals: 16.1 expected, 17.9 average, 20 actual, +3.9
4 goals: 9.0 expected, 13.0 average, 8 actual, -1.0
5 goals: 3.9 expected, 7.3 average, 3 actual, -0.9
6+ goals: 1.3 expected, 4.9 average, 1 actual, -0.3

Martin Brodeur had 4 more shutouts than expected, but 4 less one-goal games. Roberto Luongo had 2 fewer shutouts than expected, and three more one goal games. The similarity of those numbers indicates that in all likelihood it just came down to luck - Brodeur got some breaks to preserve his shutouts, while Luongo was unlucky in losing his.

Luongo was slightly more consistent than Brodeur. In 59 of his 76 starts, he gave up 1-3 goals. In terms of quality starts (2 goals against or less), the two goalies were very close: Brodeur 46, Luongo 44. Brodeur had more bad games (gave up 4 or more 0.7 more times than expected). Luongo had fewer bad games (gave up 4 or more 2.2 times less than expected). Luongo was actually also slightly more likely to let in 2 or less (1.3 times fewer than expected, compared to Brodeur's 2.7 fewer than expected).

As you would expect from two goalies with very similar goals against averages, there isn't much between them. It just reinforces that the difference in goals against average is almost entirely from Luongo facing more shots per game. If I had to pick one distribution ahead of the other, I'd go with Luongo's, although the difference is very slight.

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