Advanced stats, even relative ones, aren't perfect at really determining how good a role player on a really good or really bad team is. There's an attempt to figure it out, and it's good to look at, but like any stat, it doesn't tell the whole story.
It's possible that he in general does help the team generate more chances than they give up. But it's also possible, that in a Game 7 OT, when the team has the puck behind his goalie's net, that he doesn't do a great job of holding his ground, and when a series ending shot is taken, he kind of flinches instead of putting himself in front of it. Watch that Verhaghe goal, and you don't need any relative metrics to tell you that he didn't do his job there.
One play. Doesn't mean he sucks, but just adds to the whole picture instead of just relying on stats (which by the way I do generally like... but they aren't perfect).