Bruce over at Copper & Blue has laid out the case for Martin Brodeur as the best goalie of the 2000s. He picks Brodeur as the best combination of quantity and quality over the given time period, and describes him as a "win machine".
Brodeur's teams have won a lot of games, that is undeniable. However, the problem with using wins is that you are giving individuals credit or blame for team results. The best goalie is the one who did the most to help their team win, not the one who had their team win the most. I'm not picking Luongo as the best goalie of the 2000s because he ranks first in a few random statistics that I happen to like, I'm picking him because I think he did more than anyone else to help his teams win.
I have a method for quantifying a goalie's expected wins, based on their goal support, shots against, and team discipline. It compares the goalie's team to league average in each of those categories, assesses how many goals they scored or prevented compared to average, and then converts that goal differential into wins. Here are the averages of the key components during the period:
Brodeur's teams: 232 goals, 25.9 shots against/60, 298 power plays against
Luongo's teams: 207 goals, 31.4 shots against/60, 403 power plays against
League average: 229 goals, 28.3 shots against/60, 370 power plays against
For example, since Brodeur's teams averaged 25 more goals per season than Luongo's teams, we would expect that to translate into more wins. The standard rule of thumb is that a 6 goal differential is equivalent to one win, which means that Brodeur's teammates' offence is worth about 4 extra wins per season.
It's not too difficult to see from those numbers that it was easier to win games in Brodeur's situation than in Luongo's. Brodeur had a significant advantage in all three categories. I calculate Brodeur's teams as having 410.1 expected wins and 465.0 actual wins, counting each tie or shootout/OT loss as half of a win. Luongo's teams had 296.1 expected wins and 353.5 actual wins. If we subtract the two numbers, we can see how each team did relative to their expected numbers. Brodeur's teams won 54.9 more games than expected, while Luongo's won 57.4 more. It is even more impressive that Luongo's teams outpaced Brodeur's teams since Luongo played 80 fewer games. That's almost an entire season's worth of weaker backup goalies in net, which would likely substantially drag down the overall results.
If we convert the expected numbers into winning percentages, we can compare directly with each goalie's actual winning percentage to remove games played by backups from the equation. Brodeur's winning percentage was .630 while his teams had an expected .556, for a difference of .074. Luongo's winning percentage was .498 compared to .401 expected (+.097).
That's not the entire story, however, as there are two major variables we have to still account for. One is shootouts, and the other is Brodeur's shot prevention effect.
From 2006-2009, Brodeur's teams have gone 33-18 in shootouts, while Luongo's teams are just 18-25. If we dig deeper, we see that Luongo and his backup goalies actually had a better combined shootout save percentage (.696) than New Jersey did (.679). The difference in win/loss record is entirely because Brodeur's teammates scored on 40% of their shootouts while Luongo's teammates scored just 28% of theirs.
To factor this in, we need to adjust the expected win totals to reflect the rest of the team's shootout performance. Brodeur's teams won 7.5 more shootouts than average, while Luongo's won 3.5 fewer. Adding that to the win totals, we get Luongo's teams at 60.9 wins above expected and Brodeur's at 49.9.
Finally we come to the tricky issue of shot prevention effects. It's much tougher to assign a specific number here, so I'm going to rely on a sensitivity analysis. The goal is to identify the shot prevention effect Brodeur would need to surpass Luongo, and assess whether it is reasonable that the actual difference was that large.
First, let's look at how New Jersey's overall team wins above expected would vary based on different estimates of shots against prevented by their goalie:
1 shot prevented per game: +58.9 wins
2 shots prevented per game: +70.4 wins
3 shots prevented per game: +81.9 wins
Since Luongo's teams were at +60.9, the goaltender shot prevention difference between the two teams has to be 1.2 or more for Brodeur's teams to end up ahead. I'd say it is reasonable that Brodeur's effect relative to Luongo's is that high or higher. Keep in mind though that we are comparing Brodeur's teams to Luongo's teams, and Brodeur played in 80 more games. With these numbers it is certainly possible to make a case that Brodeur provided more total value than Luongo over the decade, but let's look at the individual numbers for each goalie:
Luongo: .396 expected, .498 actual, +.102
1 shot prevented per game: .550 exp win %, .630 actual, +.080
2 shots prevented per game: .535 exp win %, .630 actual, +.095
3 shots prevented per game: .519 exp win %, .630 actual, +.111
Here the break-even point is 2.5 shots per game. I'm willing to concede a shot prevention difference between them of 1.0 - 1.5 shots per game, and maybe even as high as 2 shots per game, but 2.5 seems a bit high to me. As a result, my interpretation of these numbers is that on a per-game basis Luongo was slightly more likely to help his team win than Brodeur. To be sure, it is very close. When the numbers are close, we can also go to qualitative factors to break the tie. I generally put a high weighting on peak play in my rankings, and in my opinion in the 2000s Luongo's peak was higher than Brodeur's.
Another consideration is that each marginal goal becomes slightly less valuable the more a team's expected winning percentage deviates from .500, . A goalie on a very poor or very strong team would not see each additional goal saved have the same impact on winning, because it is more likely to come in a blowout game. On the other hand, a goalie on an average team will spend a lot of the time in tied or close games, which means that their effect is magnified. After factoring in shot prevention, Brodeur's expected winning percentage is close to .500, which means that his marginal goals saved likely had a strong impact in terms of winning games. On the other hand, Luongo's expected winning percentage was just .396. I don't think this has a large effect on the numbers, but it is something that would be a slight advantage to Brodeur.
Depending on your assessment of the method and goalie shot prevention effects, you may agree or disagree with the evidence that Roberto Luongo helped his team win more games than Martin Brodeur. I'm still working with the method so some of the assumptions may need to be revised slightly to get a better fit. Regardless, I think this exercise should be strong evidence against the view that Brodeur far surpassed all his goaltending peers between 1999-00 and 2008-09. If Brodeur can be described as a win machine, then the same thing should be said about Roberto Luongo.