Yesterday, the Islanders acquired goaltender Jaroslav Halak from the Washington Capitals for a fourth round pick. Halak's contract will be up on July 1, so it's a trade-then-sign type of deal, so the Islanders still have work to do over the next two months if they look to make the trade payoff. With the deal, GM Garth Snow addresses the most immediate and probably the most glaring need on the team of an actual, capable NHL starting goaltender.Evgeni Nabokov's numbers and age at this point are too concerning to ask him to start 40+ games next year, and as he turns 39 in July, we may have already seen the last of him in the NHL as his numbers have steadily decreased each of the past four seasons (.922 in 09-10, then .914, .910 and .905. If you guesstimate what the next in those sequence of numbers is, it's not pretty). Nabokov's already on the cusp of being well past due in the NHL as Martin Brodeur has been for a year or two, if he's not already there. Next year, a backup role -- and that's being generous -- would be all that he's suited for.The Islanders two younger netminders haven't been able to prove anything yet in the NHL and one of them, Anders Nilsson, (presumably) just talked his way out of the organization for next year. A sub-900 SVP and iffy AHL numbers don't really strike fear in managment when you make "NHL or bust" demands.If the Islanders fail to find another goalie after Halak, Kevin Poulin might just find himself as NHL backup by default in October. And that brings us to the most important point of all this; signing Jaroslav Halak.Here's the low down on him; his career mark is a .918 save percentage, a couple points above the NHL average over the last few seasons and he's coming off a year where he posted a .921 mark. That's not nearly in the elite territory where Tukka Rask and Carey Price reside, but it's a hell of a lot better than anything the Islanders have had the last decade.Here's a fun fact; the Islanders haven't had a goaltender finish a season with better than league average save percentage since the 2010-11 season. So, we talk a lot about how bad the Islanders defense was this year, but also know that it's been a full three seasons since they've approached anything better than league average goaltending (Al Montoya, Kevin Poulin and Dwayne Roloson all accomplished the feat in that injury plagued year, by the way).And what kind of a difference can a netminder like Halak make? In theory, here's how those numbers work out.Let's use Evgeni Nabokov's season for example's sake. He faced 1085 shots this year and allowed 103 goals, giving him a .905 SVP. Now, let's assume that Jaroslav Halak faces 1085 shots and, let's also assume he is able to provide his career average SVP of .918. That would provide an estimation of 89 goals allowed, giving the Islanders an extra 14 goals kept out of the net, in a vacuum. Or, if he is able to replicate his best career season's .926 SVP, he allows only 80 goals and gives the Islanders an extra 23 goals out of the net. And remember, Nabokov only played 40 games this year, half the season, so those numbers could be even bigger over a bigger sample size (50, 60, 70 games). But the point is essentially that the Islanders -42 goal differential gets a hell of a lot better, in theory, by replacing half a season of Nabokov with half a season -- or more -- of Halak.So now, the Islanders need to sign Halak. Obviously. There's not really a valid argument for not paying him. Banking on Jonas Hiller or Ryan Miller coming here instead is foolish and, honestly, they're not significantly better players. They need to pay up and get a goaltender and have two months to figure out how to convince him that this is the place to be.Should they worry about overpaying? To an extent, sure, you don't want to give a guy a 15-year, $67 million deal. Been there, done that. LHH breaks down the various comparables here, but for me anyway, I don't know that it matters too much whether Halak gets $4 million per over five years, $5 million per over four, or $6 million over three.Garth Snow said after the trade yesterday that he currently has zero goalies for next season. When you have zero goalies, you make sure you get one.