NHL announces Vezina finalists

by Dirk Hoag on Apr 27, 2009 12:33 PM EDT in Statistical Analysis

The NHL announced the three finalists for the Vezina Trophy (best goaltender) today, which includes a rookie, a late bloomer, and a Swede just hitting his prime.

One interesting facet brought to this race is a post from Behind the Net which digs into goaltender performance using the notion of Shot Quality. In other words, based on the location from which shots are being fired, which goalies face more difficult duty?

When you correct for Shot Quality, one arrives at an Expected Goals Against figure, which is what an average goaltender would give up, based on the quantity and quality of shots faced. So how do these three contenders fare when the data is adjusted to take Shot Quality into account?

NAME	GP	Save %	GAA	Ex Sv %	Ex GAA	Diff
Steve Mason	61	.917	2.01	.904	2.33	-0.32
Tim Thomas	54	.937	1.87	.911	2.64	-0.77
Niklas Backstrom	71	.921	2.21	.919	2.29	-0.08

The table above (which reflects only 5-on-5 play) shows the Games Played, Save Percentage, and Goals Against Average for each contender, followed by Expected Save Percentage and Expected Goals Against, once corrections are made for Shot Quality. The Diff column shows how the comparison between the two GAA numbers, a theoretical measurement of how far, beyond the average goaltender, each of these guys performed.

Two things jump out here. First, Tim Thomas' results were the tops in the NHL among regular netminders (>700 minutes played). Secondly, Niklas Backstrom clearly benefited from the team skating in front of him. His Save Percentage and GAA numbers are just what you'd expect, given the workload he faced.

There are a couple of issues with Shot Quality analysis, such as the likelihood that the source data is somewhat skewed based on the individuals doing the recording, and the factors that are being used to affix Shot Quality values. For instance, this looks at 5-on-5 only, and Shot Type (slap, wrist, wraparound, etc.) is ignored. But I'm comfortable with saying that this gives us a more nuanced picture than the simple NHL numbers, which have their own limitations as well.

Steve Mason

#1 / Goalie / Columbus Blue Jackets

Height: 6-4

Weight: 212

Born: May 29, 1988

	GP	MIN	W	L	T	EGA	GA	GAA	SA	SV	SV%	SO
2008 - Steve Mason	61	3664	33	20	7	7	140	2.29	1658	1518	.916	10

There's no question that Columbus would not have made it to the playoffs without Mason's outstanding season, but he did run out of gas at the end.

Tim Thomas

#30 / Goalie / Boston Bruins

Height: 5-11

Weight: 201

Born: Apr 15, 1974

	GP	MIN	W	L	T	EGA	GA	GAA	SA	SV	SV%	SO
2008 - Tim Thomas	54	3259	36	11	7	4	114	2.10	1694	1580	.933	5

After landing a #1 job relatively late in his career, many assumed that Thomas' outstanding work from last season was either a fluke or represented his high-water mark, but he has done even better this season.