By Michael Hurley, CBS Boston

BOSTON (CBS) — If you want to win the Stanley Cup, you’re going to need a deep roster. Having one great line and one great D-pairing is all well and good, but every team this year has at least one great line.

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If a team wants to go on a long, sustainable run into May and perhaps into June, it’s going to need to get some contributions from what would be considered unlikely sources.

Whether the Bruins have that for the long haul remains to be seen. But in a must-win Game 7 on Tuesday night, in a game where their best players were largely neutralized, the Bruins had it in spades.

The Bruins’ first goal of Tuesday’s Game 7 came after some good old-fashioned hard work from the fourth line. Defenseman Travis Dermott tried to clear a puck out of the Toronto zone, but Noel Acciari stopped the puck with his midsection at the blue line to keep the puck in Toronto’s end. Sean Kuraly gained possession and drove to the net; when he lost the puck, D-man Matt Grzelcyk pinched to keep possession for Boston. Grzelcyk chipped a puck to Joakim Nordstrom, who’s got all of 19 goals to his name in 228 regular-season games.

Nordstrom fired a shot on net, likely trying to get fortunate by finding a hole in Frederik Andersen.

It worked.

The entire sequence was quintessentially fourth line, right down to Acciari making the play that allowed it to happen while not registering an assist on the goal.

And it wasn’t the only mark on the game made by the fourth line, which was comprised of Nordstrom, Kuraly and Acciari.

After surviving a Toronto onslaught in the second period, the Bruins were desperate for a goal to get some breathing room in the third. The fourth line provided it.

Acciari tapped a loose puck to Kuraly in the neutral zone in what looked like it would be a nothing moment in the game. Kuraly had two defensemen in front of him, and two forwards right on his tail. Nothing appeared to be cooking to most viewers — but the Maple Leafs on the ice might have fallen into the trap of believing that too.

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Ron Hainsey stepped up and tried to cut off Kuraly near the center ice faceoff circle, but Kuraly casually stepped around him. John Tavares reached somewhat lazily toward Kuraly as the forward skated around Hainsey.

Just like that, it was a 1-on-1 situation for Kuraly, who skated in on Morgan Rielly, put the puck to his forehand, and fired a wrister high to the glove side on Frederik Andersen. Andersen’s glove hand had been hot all series, but he could not get to this one, which was placed perfectly just above his left shoulder.

“Sean has a quick release,” head coach Bruce Cassidy said. “It’s not a heavy shot, at least I don’t think it is, but because he releases it in full stride, I think the caught the goalie a little bit off guard. It was a huge goal for us.”

Patrice Bergeron, who finished the series with three goals and two assists, had a feeling that something big was coming from Kuraly.

“I saw it all along,” Bergeron declared. “I was like man, he’s got it. That was an amazing shot. I saw the hole there. I knew for some reason, I thought he was going to do it, and he got it done. So, I thought that was a great play by him at a clutch time. He’s been doing that many times, I guess, over the last few years.”

That was, more or less, the goal that sealed the game. Tuukka Rask had to make one high-level save on Zach Hyman moments later, but from there on out, the Bruins cruised to a 5-1 victory, after a pair of empty-net goals.

Oh — and the other goal scored against Andersen? That came from the third line, with Charlie Coyle cementing himself in front of Andersen to set a screen after Marcus Johansson was given a gift-wrapped puck from Jake Gardiner behind the Toronto net.

It’s the type of depth that’s much needed at this time of year, and it — along with stellar goaltending — carried the Bruins in this critical moment.

“Terrific. That’s why they’re in the lineup,” Cassidy said. “I think we’ve got a lot of good choices.”

Now the Bruins will be moving on to face Columbus, and if they want to continue their season past the second round, they’re going to need a wealth of goals from Bergeron, Brad Marchand, David Pastrnak and Jake DeBrusk. But in moments of need, when the top lines aren’t scoring as much as anticipated, the third and fourth lines will absolutely have to be able to step up. (The 2011 Bruins got 21 goals — or more than 25 percent of their playoff scoring — from Michael Ryder, Chris Kelly, Rich Peverley and Daniel Paille.)

The likes of Nordstrom, Kuraly, Acciari, Coyle and Johansson all did that in Game 7. If they hadn’t, the Bruins’ season would most likely have ended.

Those are the stakes of playoff hockey. And through one round of the postseason, the Bruins’ bottom two lines have checked off an important box in terms of ability to contribute in crucial moments.

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You can email Michael Hurley or find him on Twitter @michaelFhurley.