The orange rally towels fluttered over the glass and landed on the ice, celebratory confetti hurled from the Nassau Coliseum crowd, taunts for the frustrated souls on the visiting bench. Washington Capitals forward Marcus Johansson scooped one onto his stick and flung it away. Forward Alex Ovechkin took a slug from a water bottle and slammed it down. Their first chance at clinching the Eastern Conference first-round series against the New York Islanders had disappeared. They had ensured the nail-biting need for a Game 7.

Before the chaos of their 3-1 loss Saturday afternoon spilled beyond the final horn, when plastic beer bottles joined the towels and a 10-man melee broke out inside the neutral zone, the Capitals draped themselves over the boards and stared blankly into the fray. Islanders forward Nikolay Kulemin had already emerged from one scrum to notch the tiebreaking goal, and now forward Cal Clutterbuck had potted an empty-netter with 53 seconds left. With their season at stake, the Capitals will return to Verizon Center on Monday night for one more meeting in this feisty, emotional, skin-tight series, for the right to face the New York Rangers in the next round.

“It’s funny, there’s not a thing that really surprises me,” Coach Barry Trotz said. “You’ve got two very determined teams, two teams that are going nose-to-nose. It’s a heavyweight bout. That’s what it is.”

The description proved apt in the dying seconds, when defenseman John Carlson flung a last-ditch puck at goaltender Jaroslav Halak and the Islanders took exception. Game 6 had already featured plenty of scrums and shoves, standard procedure with so much at stake, but with 26 total penalty minutes assessed at the 20-minute mark of the third period, it became an all-out brawl. Forward Kyle Okposo charged after Carlson. Bodies stacked in a pile, next to sticks and helmets strewn about. The normally mild-mannered Johansson swapped punches with defenseman Thomas Hickey.

Then everything got chalked up to the innate intensity of their sport.

“Not going to say anything about it,” defenseman Matt Niskanen said. “I don’t want to talk about that stuff. You want to ask me about plays in the game, sure, but not that stuff.

“It’s a hockey game. Sometimes things get heated.”

Very well, then, the plays — although even the decisive sequence began with a tussle between the benches, when no whistles blew to stop play. None blew again when Ovechkin decked his fellow captain, John Tavares, along the glass to the left of Washington’s net.

As defenseman Karl Alzner finished checking Tavares and Ovechkin swiveled his head looking for the puck, defenseman Nick Leddy assumed possession inside the left faceoff circle. Niskanen and forward Jason Chimera both charged toward him, leaving Kulemin free to dive deep and juke past goaltender Braden Holtby.

“Things always happen when something happens between the benches,” Trotz said. “Always something good or bad, depending on what side you’re on.”

For the Islanders, it meant giving themselves a fighting chance to return to this building, which will close its doors to professional hockey as the team moves to Barclays Center in Brooklyn. For the Capitals, it meant trudging into the tunnel, packing their belongings and returning home, where they lost Game 1 by three goals, won Game 2 by one goal and won Game 5 by four.

They had returned north believing that blowout Thursday night would have little bearing on what awaited them here. They insisted the fans would explode with noise and predicted a furious start from the Islanders, who had taken the first lead in four of five games during this series. They foresaw the need to weather another storm.

Less than seven minutes in, defenseman Brooks Orpik tried hunting down forward Ryan Strome inside the neutral zone, searching for a crushing hit near the visiting bench. Instead, Strome flicked the puck away just in time, absorbing contact and sparking a two-on-two rush into the Capitals’ zone. Gaining speed, Tavares scooted around Carlson into the slot, while linemate Brock Nelson battled center Nicklas Backstrom for position in the crease. In stride, Tavares fired back across his body, knifing the puck between Carlson’s ankles and underneath Holtby’s glove.

From there, the Islanders began toying with fire against the NHL’s top power play, surviving defenseman Brian Strait’s high-sticking minor and Kulemin’s cross check on Orpik. But when Tavares slashed forward Evgeny Kuznetsov with 32.6 seconds left before intermission, the Capitals pounced.

Less than five seconds remained when Carlson zipped his first goal of the series through traffic and flexed his bicep to celebrate. One orange towel reached the ice in anger, and the public address announcer warned the crowd against throwing things over the glass. Two periods later, he would warn the fans again. This time, it would do no good.

“To me, at the end of the day, the desperation level of the Islanders was just a little bit higher than ours,” Trotz said. “At the end of the day, they were trying to stay in it. Now we’re both desperate. We should have the same kind of desperation on both sides, because it’s a winner-take-all situation.”