PDO, available on Behind the Net, is a great number to use to see whether a player in a given year overachieved or underachieved. PDO is the sum of the team shooting percentage and the team's save percentage while a given player is on the ice at even strength. For example, while Player A is on the ice, if his team shoots 10% and his goalies stop 93% of the shots against, Player A will have a PDO of 1.03 (103%).
For most players, this number regresses to a mean of, as intuitively expected, 1.000 (100%). For better players, it could average to 1.01 or a bit higher, and for the worse players perhaps to 0.99 or a bit lower. For example, a player with a PDO in a season of 1.02 would be expected to take a hit in his numbers the following season, while a player with a PDO of 0.98 would be expected to improve (assuming other factors stay the same).
Off the top of my head I know that the Capitals had a relatively high shooting percentage as a team at even strength and to an extent the goalies overachieved as well (especially Jose Theodore, whose even strength save percentage was the same as Martin Brodeur's), so I expect many of the Caps to have had inordinately high years.
Typically you'd expect an average-to-below-average starting goalie to give you around .915 save percentage (remember, this is at even strength).
Excluding deadline acquisitions and players who have since moved on, only Jason Chimera looks like he might have a sustainable PDO at 1.007, and I bet his is so low only because of his time in Columbus. Shaone Morrisonn, if he were to re-sign in Washington, would probably also be able to maintain similar play, and might actually look better since his on-ice save percentage was only 0.903.
Jeff Schultz had a 1.069 to lead the NHL. Alex Ovechkin had a 1.061 to finish second. Mike Green was third, Alexander Semin sixth. In fact, ten of the top sixteen are Capitals. Matt Bradley is the lowest of Caps who started the season in Washington, started Game 7 against Montreal, and who is still under contract, and even he clocks in at a maybe-okay-for-Alex-Ovechkin-but-probably-not-Matt-Bradley 1.011. Heck, even Tyler Sloan, who wasn't that great, can be expected to take a hit since his PDO was 1.01.
Even Brian Pothier, who spent one fourth of the season in PDO hellhole Carolina, still finished above 1.02 (and looking at that chart, no wonder Rod Brind'Amour had a bad season).
The playoffs were a different story altogether, though. Keeping in mind the small sample size which allows PDOs like Tom Poti's 1.091 (tied with David Steckel for the team lead), the numbers were all over the place, and shooting percentages for the Caps went down.
At the very least it's heartening to see that Alex Ovechkin could have had a better series if his PDO was even close to normal. Instead, thanks to a certain Client, he and the Caps fell in the first round. In fact, looking at the chart, the lower Caps have low save percentages--perhaps too much Mike Cammalleri, he of the 25% shooting through 14 games? Jeff Schultz and Mike Green, top five in the regular season, just flipped sides to the bottom in the playoffs.
I'd bet that such lopsided shooting and goaltending from an opponent, especially one that was heavily outshot, will not take down the Capitals again (edit: because it won't happen again). But I'd also bet no Caps team ever has a better season in terms of shooting luck than the 2009-2010 Capitals, since, in essence, every single player who played significant time in Washington this past season overachieved. No wonder the team finished with 121 points and far ahead of the pack.
Meanwhile, the 2008-2009 Capitals scored and stopped pucks at much more sustainable rates. The 2010-2011 Capitals over the regular season will probably perform right around those 108 points and #2 offense.