I've been struggling to come up with a stat that really measures defensive ability - there's a few helpful indicators (hits, shots blocked) but they're tricky to compare, and also to correlate. I'm trying to work something out with plus/minus right now, and I'm going to see if the first set of results passes the smell test.
The idea is this: Start with plus/minus. Subtract even-strength points, and you get something that's fairly close to how many goals were allowed when a given player was on the ice. The first problem is universal when you want a small number: my score in this stat is a perfect 0.
The next step is to normalize it - divide by game played, and divide by shifts/game (we don't want 7th defensemen ramping up their scores). This gets us the player's goals allowed/shift value, which tends to be a difficult-to-understand fraction, so I think it's worth scaling it up for a full season.
The next step is to normalize it for goalies, and maybe the total team offense.