I do have playoff save percentages for every season in that period, so I had the idea of comparing how many shots against each goalie faced compared to league average in the playoffs, and using that number to estimate regular season shots against totals. From there, since we know the actual historical GAA, we can estimate save percentages for the seasons that are missing and thereby arrive at an estimated career save percentage for each goalie.
I tested this out, and it seemed to work well for goalies who consistently qualified for the playoffs, especially those who played on the same team. For example, it estimated Martin Brodeur to have a .913 career save percentage, and he is actually at .914. From the work of one dedicated Flyers fan, the one who is hosting the Hockey Summary Project, we have Bernie Parent's complete stats as a Flyer. His career save percentage in Philadelphia was .917. My estimated save percentage? The same .917.
These numbers probably make the method seem more accurate than it is, but I think the numbers are probably fairly reasonable. The system does not work well for some goalies, mainly those who had a number of seasons where they missed the playoffs or had a few deep playoff runs with one team but played the majority of their careers somewhere else. An example is Gilles Meloche, who played eleven seasons in the non-save percentage era and only made the playoffs in two of them. His non-playoff teams would have been very likely to give up more shots against than his playoff teams did, so his save percentage is probably understated. Roger Crozier is another guy whose results aren't that meaningful, since he played most of his career on bad teams but had a couple of deep playoff runs on good teams which make up the majority of his postseason participation.
Here is the complete list of goalies who faced at least 10,000 (estimated) shots against, sorted by goals over league average:
The lack of parity in the 1970s means that there is a lot of team effect included in these results. All of the guys in the top 5 played on very good teams, and their backups also did well by this measure. That's not to say they weren't good goalies, but of course they played in ideal situations.
I think Rogie Vachon, Mike Palmateer, and Dan Bouchard do pretty well here considering their teammates. If Billy Smith faced 5% easier shot quality than those guys, for example, he would be behind all three of them in career regular season goals above average. That seems very plausible to me, especially when you take into account how well Resch did in New York. On the other hand, Dryden would have needed to face 25% easier shot quality than Vachon to end up at the same level, and it is unlikely that Habs were anywhere near that good. The evidence suggests that Dryden was an example of a great goalie on a great team.
For guys like Gary Smith and Gilles Meloche just to show up at average is a strong result, since I highly doubt the California Golden Seals allowed league average shot quality against. I bet both of them were better than someone like Doug Favell, despite the 100+ goal gap between them. If Smith and Meloche faced shots that were 5% harder than average, they would rank up around the same level as Bouchard, Palmateer and Vachon.
To estimate the difference in save percentage from the best teams to the worst, we can look at the save percentages we do have. There are save percentages available from the 1970-71 season, for example, the fourth season after expansion, which gives some time for player movement between teams as well as a few years for the expansion teams to start recruiting and developing talent. The average save percentage for goalies on Original Six teams: .911. Average save percentage for goalies on expansion teams: .898. Even if we assume that the O6 goalies were 10% better than the goalies on expansion teams, which is almost certainly well overdoing it, that implies that the shot quality against was 5% easier in Toronto, Montreal, Boston, New York, Detroit and Chicago. I'd bet the true shot quality difference in those early years was probably closer to 10%.
I'm still not sure exactly how to rank Tony Esposito. His numbers are very good, at or near the top in every scenario, and yet I still feel that he was only the 3rd best goalie of his generation. Esposito is similar to Martin Brodeur in terms of playing a lot of games every year behind a mostly good defence.
The two guys who appear to have some explaining to do are Hall of Famers Gerry Cheevers and Ed Giacomin. How does Cheevers end up exactly at league average in save percentage in both the regular season and the playoffs if he was such a great goalie? And presumably Hall of Famers should not be below average in the regular season and dreadful in the playoffs like Giacomin was? I think Cheevers is in the Hall of Fame because of Bobby Orr and because Gilles Gilbert's bad playoff play made Cheevers look clutch, while Giacomin is in the Hall of Fame because of the New York media and fortunate timing (playing on an original six team right after expansion he grabbed a couple of First Team All-Star awards before the emergence of Dryden and Parent).
I think evaluating goalie play in the 1970s is all about figuring out the appropriate team adjustments, because there was so little parity around the league. It is pretty clear that Esposito, Parent and Dryden were the three best goalies of the decade (they also ranked 1-2-3 in my measure of GAA vs. backup goalies). I think it is still unclear who was the best of the next tier of starters. It's not fair to simply give that credit to whoever happened to play in Philadelphia or Long Island. I think there were a number of overlooked goalies in the next tier of solid starters who simply never had the fortune of playing with talented teammates (Meloche, Palmateer, Bouchard, Gary Smith, etc.).
When we are finally able to put together the complete save percentage record, it will be interesting to compare these estimates and hopefully break down team effects in a little more detail so we can figure out who comes next after the big 3 in the ranking of best goalies of the 1970s.