Second Thoughts

Re-framing What We Know About Save Percentage

by Ryan Lambert/Columnist

Inherently, every hockey fan knows that goaltending is incredibly important. Of course it is. How could it not be?

But something that seems to come up time and again is a misunderstanding of just how important it is, and the ability of teams to repeatedly replicate top performance year after year. Moreover, there is the dissemination of goaltending statistics which are in no way telling.

Wins are really a measure of team quality, much the way they are for pitchers in baseball; you could give up 12, but if your team scores 13, no big deal.

Likewise, goals-against average is basically just a function of how many shots your team allows; if you stop 90 percent of shots you face, but you only face 10 a game, your GAA is 1.00. And if the other goalie stops 95 percent but faces 40 shots, his is GAA is 2.00, and he lost, despite being inarguably better at his job, which is “stopping pucks.” Everything else, he has no control over.

The game of college hockey has changed dramatically over the last decade or two, with save percentages going up appreciably. In 1999-2000, the average NCAA team posted a save percentage of .895, and when you look at it by conference, only two broke .900 (and even then, just barely; Hockey East was .900 even, and the ECAC was the stingiest in the country at a lofty .902).

Over the last two seasons, the average save percentage nationwide has been roughly .909, an improvement of 14 basis points. This may not seem like a lot in theory, but in actual practice, over the course of a season, the difference is massive. In a team's 34 to 48 games or so, they now face an average of about 1,150 shots, and having goaltending that stops 90.9 percent of them means they allowed about 105 goals; a team that stops .895 allows 121. An extra 16 goals against over the course of a 40ish-game season makes it significantly harder for teams to succeed not only in their league playoffs, but also make the NCAA tournament.

Again, that kinda sorta stands to reason: The average team played a little less than 38 games last year, and giving up 16 extra goals would add 0.4 goals against per game to one's total. And when a team is only scoring about 2.79 per, even the most stats-averse observer has to understand that this would significantly decrease a team's win expectancy.

The reason all this is relevant these days is that the last few weeks have seen all sorts of polls and top-10 lists come out ahead of this season, which seem to labor under the delusion that goaltending is something which happens magically, and can be counted on indefinitely. To that end, many lists have put UNH somewhere in the top half of the country despite the loss — presumably for the season — of starting goaltender Casey DeSmith, following an arrest on charges that were particularly ghastly.

Now, even if UNH were returning their best defensemen and forwards from last season, which it is not, the loss of DeSmith alone would have a huge negative impact on the Wildcats' win expectancy. The netminder ended last season with a career save percentage of .923 over 97 games, which you'll note is significantly better than the national average over that time, as well as the Hockey East average of about .914. Going by that conference number, and based on UNH's shot volume against in his games, DeSmith saved his team four goals over an average Hockey East goaltender.

That, too, doesn't sound like a lot, but the math over the last two seasons shows that every 6.4 goals of goal differential makes up a full win (that is, if you have a plus-64 goal differential, you should have about 10 more wins than the NCAA average), meaning DeSmith singlehandedly added to UNH's chances to win every night significantly. We all understand this intrinsically, but now we have to consider that the dropoff from DeSmith to UNH's next-best options (Jamie Regan and freshman Adam Clark) is dramatic.

The issue is that we had no basis to determine how good either is, because Regan, a junior, has just 6:38 to his career time on ice and didn't face a shot. Likewise, Clark is a 21-year-old freshman whose save percentage in the BCHL last season (which, granted, isn't exactly a goaltending league) ranked 13th. It's reasonable to say that in a best-case scenario, these two goaltenders would combine to give Dick Umile's club NCAA-average goaltending.

UNH already gave up more shots than most teams in the country last year, and that was with their more quality defenders, so these two relatively unheralded kids — who apparently worry the team so much that Umile is looking to bring in Danny Tirone at midseason — could also be under siege. A .909 save percentage against the 1,200 shots the Wildcats conceded last year would set the team back significantly, and again, you have to imagine that's a best-case scenario, especially if the team cannot possess the puck as effectively as it did last year (52.48 percent of all shots).

Consider that Regan was a secondary option even to Jeff Wyer, who had a career .901 save percentage, and you have to think that Clark is The Guy in Durham until he plays himself out of a job. The Wildcats better hope he can even tread water in Hockey East, because the time Tirone comes in, it might already be too late.

However, it should be noted that to this point, Clark has conceded six goals on 84 shots, good for a .929 save percentage. You absolutely take that, and despite UNH's 1-2-0 record, you'd have to say that the goal scoring (seven in three) is what's holding the team back. Scoring was an area in which the Wildcats were expected to struggle, and the only thing keeping them from being run out of the building in each of these first three games has been Clark. Can it last? The numbers suggest that the answers can't be yes; goaltenders typically don't come to college and tack 15 points onto the save percentage from their junior careers unless the team in front of them is astonishing. Which UNH is not. It's very reasonable to expect a step back in this area, meaning that even if UNH starts scoring more, the goaltending probably won't be there. This is pretty basic math at the end of the day: You can't outperform your talent all year (a concept we'll explore next week when we talk about regression).

One team that could tell UNH all about the perils of poor goaltending is just a little ways south. Merrimack last season posted an .890 save percentage, about 26 points below conference average. Thus, their exemplary shot suppression (just 885 against in 33 games) combined with their alarming shooting (goalies stopped .937 against them!) basically put a bullet in the Warriors' campaign.

Hockey East is certainly the toughest league in which to succeed in terms of shooting and stopping the puck; its league-wide all-situations PDO was the highest in the country at 100.7, and that wasn't all luck — something we'll dissect in a look at some other stats later this year. Mark Dennehy knows, and knew, full well just how important goaltending is to making teams even competitive with their competition.

“If you look at the best teams in our league, the teams that got out to the best start, they're all being led from the net out,” he said after a game at Fenway last season. “You can go back and look, but my senior year [1990-91] Scottie LaGrand led Hockey East with a 90 save percentage. He was the only one above 90. Now, if you're not 92, we're going, 'Next.' You need your goaltenders to be in the 92 range if you want to have a chance to win games at this level.”

That's certainly true of Hockey East, and in other conferences to a lesser extent (the Big Ten was the only one with an average save percentage of more than .906). If Merrimack can get anything passable out of Rasmus Tirronen this time around, who was sub-average with .908 in 25 games last season, then the ability to limit shots that effectively could go a long way toward making them a much more credible team in the conference; national-average goaltending would have seen them allow 17 fewer goals. So far, Merrimack is 3-0 because Tirronen's save percentage is .943 (four allowed on 70 shots), but one must keep in mind that they're playing low-shooting-talent clubs like Holy Cross and UConn.

Will they be good enough to do damage? Not if that shooting (6.32 percent last season, costing them about 28 goals of goal differential against the national average, and 6.25 so far this year) stays as-is, but Tirronen could start to bridge the gap between Merrimack and the middle of the pack in Hockey East even if he comes back to earth somewhat.

When you're putting together predictions and polls for a season that hasn't started yet, the only data you have to go on is who's coming in, who's coming back, and who's gone. The indications are that who's coming in for UNH isn't good enough that the coach is willing to stick with him or the guy who's coming back for a full season. As for who's gone, well, it seems he was being counted on to make a world of difference. The difference between Dennehy's ideal “.920” goaltender and even a .909 one is big enough that it makes a substantial difference in team performance, and it doesn't seem as though Umile is counting on getting even that much.

As a result, any bet on UNH to repeat last year's success is probably an unwise one.