For a long time, (over 2 years), I've been banging the drum that Evgeni Nabokov was a bad goaltender. In fact, through 21 games, I noted that Nabokov was terrible and had cost the Islanders 10 goals (about 3.33 standings points) compared to an average goalie at that time - his EV SV% was .890 - .030 worse than the average (and .033 worse than the average starter). Still, the Isles held strong, and Nabby greatly improved his play, posting an elite .935 evsv% in the remaining 24 games that he played. In that period, Nabby saved a little over 5 goals over the average goalie (1.66 standing points roughly).
So there was a great debate over whether Nabby was truly an issue or whether he had turned the corner. And then the playoffs happened: 6 games, .863 evSV% - costing the Islanders 7 goals in those 6 games alone worse than the average tender.*
*Do note that the average tender faces offenses not quite as good as the penguins in the regular season, as Nabby did for those 6 games. Still, even at .910, which would be atrocious for regular season, Nabby would've let in 5 less goals than he did in the playoffs.
Suddenly Nabby was thought to be horrible and a major problem by the fanbase, who were stunned when the Isles not only re-signed the goalie, but actually gave him a 500K raise. Isn't he going to prevent the team from making the playoffs again?
The answer....might surprise you.
How bad is Nabby Really? Evgeni Nabokov is clearly a below average goalie. But how bad is he really? Let's get a quick estimate. Over the last two years, Nabby has a .9165 EVSV% on 1930 shots. We're using two years of data here because last year's sample of under 1000 shots is basically nothing for a goalie - in general, goalie sample sizes under 2K shots are near meaningless and we'd probably prefer 3K or more if we could get them. But here we only have 2 years of Nabby data for just under 2K shots, so this will have to do.
Now .9165 is not good. NHL average has basically hovered around .919-.920 over the last 3 years for goalies, with starters being closer to .923. Over a typical season, that means Nabby will cost the Isles 5 goals (on 1500 shots allowed) that an average goalie would've saved. That's less than 2 standing points - not something a team can't overcome. It's 3 standing points compared to an average starter - but again, survivable.
Even adding in the playoff data doesn't change Nabby much - he becomes a .9133 goalie, which costs the Isles an additional 5 goals and thus makes the Isles 3-4 points down due to goaltending. Now we're hurting if the Isles are a fringe team, but not THAT much and the playoffs exaggerate Nabby's badness since we won't always be playing the Penguins.
In short, Evgeni Nabokov will hurt the Isles a little bit in their chase to make the playoffs yet again, but isn't that big of a wall.
That DOES NOT MEAN that goaltending isn't a problem.
Nabokov was a .916 EV Goaltender last year. But the Islanders weren't a .916 EV SV% team. Instead, they were a .910 team! That's another 4 goals they lost over 48 games, and well, over a full season, .910 goaltending is 11 goals worse (nearly 4 standing points) than .916 (just Nabby) and 19 goals worse than an average tender for the whole season (a little over 6 standing points). Six standing points is kind of huge.
The reason is that there was no backup for Nabby at all:
Poulin: .906 in 4 Starts and 5 games
DP: .833 in 3 games and 3 starts.
And here's the problem: the Isles haven't fixed this in the offseason either, they're merely hoping that Poulin (or Nilsson) will be serviceable. But neither has a track record of being so or are clearly going to be so - Poulin was actually just as bad in the tiny 11-12 sample. Several guys who are likely at least solid backups - Khudobin, LaBarbara etc. - signed for cheap in the offseason (a million or less) and the Isles didn't pursue.
Honestly, I'd bet Poulin can probably manage .910 instead of .906 - but that's still not great at all. And its' an issue especially given the good deal of back to backs this season due to the olympic year. The backup goalie for the Isles is likely to get 20 games of play - at the least. Incompetence there can be crushing.
In short: Nabby is a slight problem for the Isles, but GOALTENDING is a big problem because the Isles have no one else.