The problem with statements like that is that it lacks context. A 'league average backup' isn't playing behind the kind of defense that has regularly been iced when Stalock plays. A 'league average backup' isn't changing the defense's tendencies to suck when the backup is in net and that level of a goalie is also not making any more saves against the types of chances given up in the games Stalock has played.
People need to bury the idea that you can just put so and so there and the numbers improve. It's nowhere near that simplistic.
I'm not of the belief that defense destroys a goaltender's play over a span of 30+ games, only in much smaller sample sizes.
I've been hearing for years that the Oilers goaltenders suck because their defense is bad. In reality, part of the reason their defense (as in goals against) is so bad is because their goaltending is weak as hell and they go dumpster diving or shopping at dollar tree for their goaltenders. Same with Arizona too. But Lindback has stunk on ALL 3 teams he's played on in the last 4 years and Smith was always a mediocre starting goaltender. Lindback was terrible for Tampa Bay and Bishop has been solid. The other goaltenders there have been good too, outside of Nabby's skeleton.
There's just as many BAD teams with horrendous defense, that actually have goaltenders playing well. Jonathan Bernier was amazing for one year behind a 35+ shot against Toronto. Now they have some structure and are playing respectably and he looks like a sieve that can't stop a half a mile per hour beachball from 100 feet out.
Ottawa is a good example too. They have averaged well over 30+ shots against the last half decade+ and Anderson has been awesome for the most part for them. With just one mediocre year in there.
As a Devils fan, the Devils were a mess last season and Schneider was absolutely amazing. It didn't get the team into a playoff spot, but it sure kept them from picking second or third overall and they looked respectable in the goals against category.
At some point, the defense needs to stop being blamed. Both guys play behind the same defense and one has been much better. Of the 3 goaltenders that have played for this team in the last 2 seasons, 2 have performed at an above average level, while the other has been below average at best. Not counting Grosenick, as he only played 2 games.