It's tough to look at the Columbus Blue Jackets right now. Statistically, they're continuing to deal with team-wide failure. Rick Nash only has the 77th highest point total in the NHL and is off his career average totals per game (certainly not inspiring to outside fans during Nash trade discussion). Overall, the team is 28th in goals for per game, as anemic production is not limited to the captain. Clearly the Jackets are in need of some serious offensive help if they hope to be future playoff contenders.
But lately, much of the focus has been on the goalie and the defense. Why should we look at them instead of the pathetic goal scoring? By doing an overly simplified thought experiment, we can look into why terrible goaltending is something that the rest of the team can't be expected to overcome.
In order to do this, let's set up some numbers. Steve Mason (as of this writing) has a season save percentage of .887. For his career, he's now at .903, a sizable dip from his Calder Trophy campaign. While it's not fully accurate to his performance this year, we'll assume he's got a .900 save percentage; that is to say, a goal would be scored in 1 out of every 10 shots against him (.887 would make the total slightly higher). Let's also consider the Jackets' shot totals. Currently, the Blue Jackets allow 30.1 shots against per game (that's the 14th fewest per game by a team in the NHL - a reasonable placement). Let's make it easier and say they allow exactly 30.
Now let's imagine a typical Blue Jackets game with the regular number of shots against, and Steve Mason in goal. 30 shots are allowed and 1 out of 10 shots is a goal. That's 3 goals against per game. 3 goals seems like quite a bit to allow to the other team every game. And that knee-jerk perception is correct.
Currently, only 6 teams in the NHL score more than 3 goals per game on average (actually up from 4 teams last year, and 5 teams the year before). Those teams are Philadelphia (3.31), Boston (3.27), Vancouver (3.16), Chicago (3.08), Detroit (3.05), and Pittsburgh (3.02). This kind of scoring helps explain why the Flyers and Blackhawks are in the playoff race despite their well-documented goalie problems. This also suggests part of why the Jackets can't win with Steve Mason in net - like most teams in the NHL over the past 3 seasons, they simply do not have the offense to keep up with an opposing team that scores 3 goals per game.
What would happen if we put a better goalie in net? Let's say that this year's version of Curtis Sanford is starting with his .915 save percentage. That would result in 2.55 goals against per game (on 30 shots). That's a pretty big difference in offense and is much more manageable. 18 out of 30 teams in the NHL are capable of that kind of scoring, so it's not uncommon. Improve the goalie by just that much and the Blue Jackets would be far more competitive. That's a part of why the Jackets have been more successful in front of Sanford. (And for laughs - if we put Henrik Lundqvist's .941 in net, that's only 1.77 goals against per game, something even this year's Blue Jackets could beat.)
Of course, this analysis is highly simplistic. It ignores the awful defense, and any psychological failures in front of Mason, something that most "better" goalies this year don't have to deal with. This also doesn't account for the Jackets pathetic goal scoring. Columbus would need a goalie with a .925 save percentage to get wins with their current offensive production. But the problem presented by Steve Mason is a real one - only 6 teams can be expected to keep up with the 3 typical goals his save percentage allows. Even with an improved offense, it would be very difficult for the Jackets to win when opposing teams are afforded such high goal totals. That's why goaltending is so heavily linked to the Columbus failures; with just one bad player in net, the whole team must suffer the consequences.