When the Islanders doted a 15-year contract upon unproven goaltender Rick DiPietro, it earned them derision from hockey pundits across North America. When DiPietro lost three straight games and then went down with a groin injury during the Isles’ season-opening West Coast road trip, the naysayers didn’t have to wait long to say their “I told you so’s.”

Making the story even juicier, backup Mike Dunham — a former NHL starter who made the team after signing a preseason tryout contract — won two straight games, sparking conjecture that perhaps a goaltending controversy could be the next drama to unfold on the Island.

But to suggest that goaltending has been the key to the Isles’ season thus far would be to deny reality. For in truth, the Isles will only go as far as their self-discipline allows them. Looking back at the first six games of the season, the turning point more likely came not when Dunham took over for DiPietro, but when the Isles’ seemingly endless parade to the penalty box came to a sudden halt.

Throughout the first four games, the Isles were significantly less disciplined than their opponents, taking 78 minutes in penalties as compared to their opponents’ 40. By spending an additional 38 minutes shorthanded — nearly accounting for two of the season’s first 12 periods — it should have come as little surprise that they got off to a rocky start.

Their undisciplined play reached its apex as the road trip came to an end, when the Isles spent 10 minutes in the sin bin in the final period of their 5–4 shootout victory over the Anaheim Ducks. Without a doubt, Dunham kept them in the game, and his performance in the shootout became the prevailing storyline, but the late-game heroics wouldn’t have been necessary had the Ducks not tallied two power play goals during that ugly third period.

But there were signs during that game against the Ducks that the Isles were starting to turn things around.

“After the first period against Anaheim, when the Isles were thoroughly outplayed, they made some adjustments heading into the second period where they took away the middle of the ice from the Ducks,” new Islanders color commentator for FOX Sports NY., Billy Jaffe, said. “The Ducks had been beating them with their speed, and they made some adjustments and scored three goals. Now granted, they had to hold on to win that game, but to me, that was the indication that the team could make adjustments and play smarter.”

The lack of self-control continued during the first period of Saturday’s home opener against the Boston Bruins, with the Isles getting whistled for four more minor penalties (giving up a power play goal to go down 1–0). But in the final two periods of that game, they took only one more penalty, while the Bruins were called for eight. While Dunham was again excellent in turning aside the man-advantaged Bruins during that frightful opening period, the reason the Isles came away with a 4–1 victory was because they finally exercised some discipline.

In Monday night’s 2–1 shootout loss to Nashville, the Isles and Predators were each called for only two minor infractions during the entire game. And while that loss was surely frustrating, for the Isles to have played a Cup contender that closely was a very good sign for their future.

When head coach Ted Nolan was brought aboard, it was expected that the Isles would employ a more hard-hitting brand of hockey. But while physical play and aggression can be a great asset to a disciplined team, they can also precipitate the rapid undoing of a team lacking self-control.With NHL officials calling games as tightly as ever, careless use of the stick — and the power plays that inevitably ensue — will be the tipping point in virtually every game.

Last season, DiPietro posted a .844 save percentage while the opposition was on the power play. During his time with the Atlanta Thrashers, Dunham was only slightly better, at .846. In sharp contrast, the Rangers’ Henrik Lundqvist posted a .899 save percentage while shorthanded, best amongst NHL starters and a critical reason why the Blueshirts made the playoffs.

Dunham’s save percentage is currently a gaudy .953,and his success rate against opposing power plays a stellar .909, but that’s unlikely to hold up. And despite battling through a groin injury, DiPietro’s save percentage while shorthanded (.860) is actually an improvement over last season’s. So assuming the goaltending slips a bit — in Dunham’s case, a virtual certainty — then the key to success will have to be disciplined play.

Tonight, the Islanders will face a huge test when they host the Pittsburgh Penguins at Nassau Coliseum. The Pens are a team on the rise — far better than they were last season — and they boast one of the NHL’s most lethal power plays. Featuring Sidney Crosby, Mark Recchi, Evgeni Malkin, Sergei Gonchar, and Ryan Whitney, the Pens’ power play is absolutely fearsome.

If the Isles can stay out of the box, they’ll have a good shot at beating their defensively challenged division rivals. But if their self-control is lacking, look for Crosby and company to have a field day teeing off on Dunham.

Taking a longer view, there wasn’t much reason to expect this Islanders team to be a Cup contender. But it’s important that they take a huge step forward this year under Nolan’s stewardship. They need to define who they are and what type of game they play, and the last five periods have been a very good place to start.

Mr. Greenstein is the editor in chief of InsideHockey.com.