There's a cute baseball acronym among some baseball circles: "There is No Such Thing as a Pitching Prospect" (TINSTAAPP). The idea behind the saying is that pitching prospects, or really pitchers in general, are so incredibly difficult to predict due to the frequent injury rate and random events that cause a loss of performance (a random velocity drop or loss of control, for example), that to call a player a pitching prospect is just silly....because odds are so good (especially compared to hitting prospects) that they will end up being irrelevant.
The same is true in hockey with goaltenders. You'd think Islander fans would be more cautious on this due to history, but the answer appears to be no, as seen by a recent fanpost asking for an extension for Al Montoya. Let's make this clear:
You CANNOT Predict a Goaltender's Future Performance, or tell how good a goaltender really is, from less than MULTIPLE (Re: At least three) Seasons of Data.
Why is this, you might ask? Well, it's because goaltender numbers come from really small sample sizes. First, remember that you have to separate out even strength numbers from PP or PK numbers - a goalie whose team is constantly PKing will have worse numbers, though no fault of his own, and this doesn't mean he's a worse goalie. Then remember this: A large percentage of shots on goal have no chance of going in and are easy saves, that aren't dangerous at all. I don't know the exact number on this percentage, but I'm sure it's well over 50%. That's why all goaltenders, even the worst ones, post save percentages over 80% and most are at least around the 90% mark. So we're dealing with around 5-10 shots on goal per game at most that are actually going to give us an idea of a goalie's true talent and performance.
The end result of this is that goaltender seasons tend to fluctuate greatly. After all, if a goalie simply has a hot streak for 10 games, and has less of these tough shots, and saves them all (which will happen every now and then), his SV% for those 10 games can look incredible, even if he's a mediocre goalie. A few extra saves in a few games results in a player looking a lot better than he is, due to the small sample size. To quote Behind The Net Hockey's Gabe Desjardins:
We have 13  goalies who were called up and posted a .925 save percentage or better in their first 15 games. But over their next 60 games, they posted a very pedestrian .906 save percentage, which would seem to be a huge disappointment for guys who started out so hot. Given that the difference between an All-Star .920 goaltender and a replacement level .900 goaltender is one goal every other game, 15 games is not a large enough sample size to be confident in a goaltender's abilities - one out of every six .900 goalies will out-perform a .920 goalie over a 15-game stretch.
-BehindtheNet, February 23, 2011
Here's the more-amazing thing: Even a single season isn't enough to truly tell if a goalie is good or not, or if he's just lucky. It's very possible for good goalies (see Tim Thomas and Carey Price) to have "down years," when what really is occurring is just random variation in a small sample size causing them to appear to have lost all of their skill at goaltending. Similarly, a goaltender can look amazing over a single season, only to then collapse (see Steve Mason)....with his amazing season not being due to him being an actual elite goalie, but just due to utter and absolute luck.
Islander fans should be very familiar to this phenomenon. Here are the statistics of an Islander Goalie of the Past:
|Season # in the NHL||GP||SV%|
I'm sure you can guess who this goaltender is: It's Rick DiPietro. Now here's the truth: It's very possible that Rick DiPietro's drop off from his .919 SV% was due to playing injured. Totally true. But what's also the truth is this: It's very likely that the .919 was also somewhat of a fluke. After all DiPi never before put up such crazy numbers in an NHL season, with him having a mere .900 SV% the year before hand. It could be that DiPi truely was an elite goaltender before being injured.....but it could also just have been a total fluke season.
In reality, you need probably at LEAST three seasons of data on a goaltender before you can make a snap judgment as to a goalie's value. Looking at multiple seasons, we can see that there are only a few goaltenders who can be considered elite: Thomas Vokuon and Roberto Luongo with Ryan Miller and Tim Thomas seeming also to be up there (Brodeur was up there prior to this year). There are a lot of goaltenders who seem to simply be average and who have great years and bad years in their career. This isn't a bad thing btw: you'll notice that the teams that have won the cup recently have done so with merely average netminders, rather than with the newest version of the Dominator.
Itis a frustrating thing, really, to have to wait for multiple years of results to make any judgments, because one wants to look at a season with clearly better results as a showing of a player growing and improving, and becoming a better player. But with goaltenders, we simply cannot do that: the increase in performance is more likely to be a fluke than simply a player growing into his potential, and we need to be patient and wait for confirmation that the results are real. From what we've seen this year, in the NHL or in Bridgeport (for Poulin), we CANNOT say that either Kevin Poulin or Al Montoya are the real deal, and thus the team must proceed with caution.
It'd be nice for the Isles to say they have 4 goaltending prospects in the pipe, at least one of whom is likely to become the elite or above average goalie who will lead them to glory. But remember the real truth - odds are none of the goaltenders will be elite, and probably not more than one (if one) will be an average NHL goalie.
The reality is: THERE IS NO SUCH THING AS A GOALIE PROSPECT.