Friday, January 8, 2010

Puck Prospectus: The Best Goalie in 2009

Here's a link to my Puck Prospectus article on the best goalie in the calendar year of 2009. Spoiler alert: It's the guy I said wasn't worth his contract in this post from the summer of 2008. Whoops. Actually, in my defence, I said that he had to improve on his play to be able to justify his paycheque, which I think was probably a true statement at the time, and Miller certainly appears to have done that over the last 12 months.

I just wanted to throw in a few comments about the Sabres and shot quality here, since they are relevant to Miller's performance. The debate continues over the significance of shot quality measures and as such I think it's a topic that is worth investigating. I'd say that the immediate post-lockout Sabres are one of the most interesting case studies for shot quality analysis, because there seems to be a discrepancy between what one would intuitively expect and what the shot quality metrics claim. The shot data says the Sabres have tended to allow easier than average shots against, but with the offensive style that Buffalo played up until this season I think the general perception was that Miller was often being hung out to dry.

I wonder if a higher percentage of shots and goals against came on the rush for the Sabres in those seasons. The team was certainly shooting the lights out themselves, which indicates that they were creating some pretty good chances, and several of their players reached scoring levels that they hadn't reached before and haven't matched since. That suggests some kind of team effect, and it seems reasonable to me that a high-event team would see the percentages go up at both ends of the ice, just like a conservative low-event team would likely make the job easier for their own goalie in exchange for creating less offence at the good end of the rink.

I also suspect that Buffalo didn't play much to the score defensively, especially at home, and kept pushing for goals. From 2005-06 to 2007-08, the Sabres scored 3.67 goals per game at home and allowed 2.84 against. On the road, they scored 3.04 and allowed 2.89. That's a 21% scoring jump at home with almost an identical defensive record. Compare that to an average team, which scores 11% more at home and allows 11% fewer goals against. In 2006-07 the Sabres won the President's Trophy while allowing the fourth-most third period goals against of any team in the league. To put that into context, the last two President's Trophy winners both allowed the fewest third period goals against in the league. At the same time, the Sabres were also shooting the lights out late in the game, as from 2005-06 to 2007-08, Buffalo's lowest rank in third period goals scored was 4th.

This year Buffalo is tied for third in fewest goals against in the third period. Buffalo's third period goal distribution (+41/-29) is in fact identical to that of the New Jersey Devils. Without knowing the shot totals it is tough to say how much the goaltending has to do with that, but that's quite uncharacteristic for post-lockout Buffalo. Over the past three seasons the most similar team to the Sabres in third period scoring has been the Carolina Hurricanes, not exactly a team that anyone would confuse with the Devils. The Sabres are also 17-0-0 when leading after two periods in 2009-10, which is quite an improvement given that closing out games is something that the team has been pretty mediocre at over the last three seasons.

Perhaps there is a shot quality effect that isn't being accounted for in terms of rush chances. Time and space affects shot quality, both in terms of allowing the shooter to make a better shot as well as giving him more available options for the defensive team and goalie to worry about and try to defend against. We know that power play shots are more likely to go in than even strength shots from the exact same spot on the ice. That is likely because the shooter has more time and space to make their shot, and that the power play team can use quick puck movement to create a more difficult scoring chance for the goalie. Those same factors are why odd-man rushes are also dangerous scoring chances.

It wouldn't be possible to identify every rush chance from the play-by-play records, but I wonder if goalies see their save percentages drop if they face a shot against within, say, 8 seconds of a shot at the other end of the rink (adjusted for scoring location, of course)?

I'd say that the statistical evidence suggests that Miller has improved his game lately from where he was a few seasons ago. He looks better to my eye this year as well. It remains possible that there were some team factors that exaggerated his apparent recent jump from good to great. I would welcome the input of any Sabres fans if they have any additional insights on the post-lockout Sabres' play, shot quality, and its possible impact on Ryan Miller.


JLikens said...

Vic Ferrari made a post a couple of months back that examined shot recording bias in terms of shots directed at the net vs. shots recorded at various NHL arenas during the 2008-09 season.

HSBC, the home rink of the Sabres, was one of the arenas that exhibited bias. It appears that the shot recorder in Buffalo is more likely to consider a shot directed at the net to be a 'shot on goal' when the shot is taken by the Sabres opponent, and less likely when the shot is taken by the home Sabres.

For example, in Buffalo road games, some 58% of the Sabres shots directed at the net were recorded as shots on goal, whereas only 53% of the shots directed at the net by the Sabres' opponents were counted as shots on net.

In Buffalo home games, however, the corresponding figures were 58% (for the Sabres) and 61% (for their opponents).

Consequently, it would seem that the save percentage of Sabre goaltenders may be inflated by the shot recording tendencies at HSBC.

JLikens said...

I just checked Miller's home and road splits from the last couple years and his home save percentage doesn't appear to be appreciably higher than his road save percentage. In fact, the opposite appears to be true.

So my above post might not be capable of explaining all that much.

Derick said...

Interesting fact about evaluating goalies: Since the 1964-65 season when the Conn Smyte was first awarded, a goalie has won the Conn Smythe 14 times. In that same time span, the Hart was only won by a goalie 3 times, Hasekx2 and Theodore. Even going back to when the Hart was first awarded in 1923-24, a goalie has won the Hart 7 times, half as many in twice as long.

My best guess why is that, because only one (possibly two) teams are considered to have achieved their end in the playoffs, while in the regular season more than half of the times involved did, the team success bias is much stronger, and if the best player isn't on the best team, it's easy to take it for granted that the "most important position" is why the team won.

I haven't measured this, but I recall that goalies often win the Conn Smythe when the playoff's leading scorer isn't on the winning team. A sort of default second choice in that case, perahsp?

Tom Awad said...

Hi CG,

I think your analysis was, and is, spot-on. Miller was pretty terrible during the 2007-08 season, right before the Sabres re-signed him, and was good but not great last year. My own analysis is that the Sabres have been pretty close to average in shot quality against the last 3 years, and either way you can't "team effect" your way from 0.906 to 0.936 on the same team in 2 years. Miller's current elite level was unexpected. For every Miller contract that you decry and will be wrong on, there's a Cam Ward who proves you right :)