So what about zone starts, quality of competition, and quality of teammates. What about on ice save % both for and against? There are so many variables that simple +/- doesn't take into account.
For instance, Alex Edler last year. He finished a -39. He must have been the worst guy ever. Except, the opposing goalies had a save % over 96% while he was on the ice. Just dumb luck unless you think Edler had the power to make all of his teammates suck at shooting while he was on the ice.
Or how this one, both from the same team.
Player 1 had a +39
Player 2 had a +38.
Player 1 started in the offensive zone 20% more often than Player 2.
Player 1 also gave up 400 more shots than Player 2, while getting fewer than 100 more shots than when Player 2 was on the ice.
Clearly, +/- isn't telling the whole story with these two. (Krejci is player 1, Bergeron is player 2)
Ok, one more, both defensemen.
Player 1 has an even rating.
Player 2 is a +4.
Player 1 gets 41% of their starts in the defensive zone, and less than 25% in the offensive zone.
Player 2 gets more starts in the offensive zone than in the defensive or neutral zone and is not one of the defensemen the team relies on in tough defensive situations.
The team is shooting about the same amount of shots as they are allowing when the two are on the ice.
Player 1 is the crappy playing Seidenberg from this year. Player 2 is the defenseman that is dominating your ratings.
edit: I'm hoping this comes off as helpful and not like I am being a dick. Its not intended to be dickish. I hate it when people on this board (or the internet in general) are like that.