Few rivalries in all of professional sports can match the intensity and passion that has marked the blood feud between the Rangers and Islanders. Sparked for perpetuity when Isles defenseman Denis Potvin’s check broke the leg of Rangers forward Ulf Nilsson back on February 25, 1979, this rivalry has a seemingly endless supply of vitriol and hatred.

Whether it was Isles center Pat LaFontaine leaving the Madison Square Garden ice on a stretcher back in 1990, or the more recent memory of Chris Simon taking a baseball-bat swing at the Rangers’ Ryan Hollweg last spring, the ugly side of this rivalry has never feared to rear its head. And that can certainly be said for the fans as well. LaFontaine’s ambulance was rocked and pounded by fans as it left the Garden. Potvin’s name was forever immortalized in a profane chant that has become a Garden tradition, even though many of the most vocal participants probably aren’t aware of its origins.

But this rivalry has also been defined by the high-energy hockey that can always be expected when the two teams go head-to-head, and that is as much a reason as any why it remains such entertainment. The Rangers and Islanders have met on eight separate occasions in the NHL playoffs, with the Isles holding a 5–3 edge in victories, including four consecutive wins from 1981–1984. With the current NHL schedule pitting them against one another eight times each season, familiarity only heightens the contempt.

Tonight at the Garden, the two teams will take the ice for the first game of a home-and-home series (they play at Nassau Coliseum on Thursday night), and the consequences are particularly severe for the Islanders.

“The make-or-break point is definitely here,” Islanders head coach Ted Nolan said after his team’s shutout loss to the Panthers on Sunday, when they failed to score a single goal despite firing 53 shots upon Florida netminder Craig Anderson. He couldn’t be more right.

The Isles are currently in last place in the Atlantic Division, but more importantly, they are five points behind the Philadelphia Flyers (who have one game in hand) in the race for the eighth and final playoff spot in the Eastern Conference. All season long, the Isles have been defined by their unfailing effort, their lunchpail squad constructed in Nolan’s image accomplishing more with less than perhaps any other NHL club. But if their slide continues and they miss the postseason, their tremendous effort will effectively have been for naught.

Meanwhile, the Rangers are on an impressive 7–0–2 run, and have lost in regulation only twice dating back to January 31. During that stretch, they’ve pulled away from the pack a bit, opening a five-point lead over the ninth-place Buffalo Sabres. But their postseason reservation is no certainty yet, and they’ll need to play well down the stretch not only to secure a playoff spot but also to maintain their positive momentum once they get there.

If the Isles, who have lost four of five games following a six-game winning streak, are to turn things around, it’ll depend largely on the play of All-Star goaltender Rick DiPietro. Last season, his 15-year, $67.5 million contract was a target of league-wide derision, but DiPietro has emerged as a stabilizing influence, masking the team’s many defensive flaws. He can expect to be the target of near-constant jeering tonight, and how he handles the adversity will certainly go a long way toward determining the game’s outcome.

Interestingly, though the Rangers boast a far more talented lineup than the Isles, their success depends largely upon the play of a goaltender who was widely overlooked as a pre-draft prospect. Selected with the 204th pick in 2000 (the same draft in which DiPietro went first overall), Lundqvist’s ascension to the starring role between the pipes for the Rangers was anything but predictable. In 2004, the Rangers used the sixth overall pick in the draft to select netminder Alvaro Montoya, perhaps unaware of Lundqvist’s potential.

Lundqvist, of course, was a Vezina Trophy finalist in each of his first two seasons with the Rangers, backstopping the team to the playoffs in both years (ending the Blueshirts’ lengthy playoff-less drought), while Montoya’s progress stalled a bit during his time with the University of Michigan and the Rangers’ AHL affiliate in Hartford. Without question, Lundqvist’s recently signed six-year, $41.25 million contract extension paved the way for last week’s unceremonious dumping of Montoya in a low-profile deadline-day deal.

Lundqvist has played fairly well against the Islanders this season, posting an impressive .914 save percentage and 2.28 goals-against average, but the Rangers have lost three of the four games nonetheless. And with four games remaining in the season series, these games will play a critical role in both teams’ respective fates.

No animal is more dangerous than when cornered, and that’s exactly what the Islanders are right now — their backs are against the wall and their season is effectively on the line. Regardless of their place in the standings, the Islanders always play their best when lined up against the Rangers. Given the current situation, look for nothing less tonight.

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