The second line of Taylor Hall, Erik Haula and David Pastrnak needed only six seconds in Boston’s 4-2 victory over the Florida Panthers on Tuesday night to show how potent it can be off the rush.

The first strike started in the defensive end. Hall carried the puck laterally through the neutral zone, avoided a check from a stepping-up Radko Gudas and made a pretty pass to Pastrnak, who all of a sudden had a two-on-one with Haula. The centerman buried Pastrnak’s nifty backhand pass.

The second goal came right off the ensuing faceoff. Hall poked the puck away from MacKenzie Weegar to Pastrnak, who in turn sprung Hall for a breakaway goal.

It was a beautiful blitzkrieg. But those rush opportunities may not always be available come playoff time, as Hall learned last year and as Coach Bruce Cassidy has been preaching to the line.

“It’s just the way it is,” said Cassidy on Wednesday. “Players are more committed, they manage pucks better, they reload harder, they’re just more accountable defensively through the neutral zone. So they have to be able to score different ways than off the rush. And they’ve done a good job. (Tuesday) night they scored off the rush because of their speed and quick strike (capability), and those are still going to be there at times. But they’re not going to get as many of them.”

Hall’s line with David Krejci and Craig Smith had given the Bruins a major boost down the stretch last spring. But when they hit the grind of playoff hockey in the second round against the New York Islanders, that second line production dried up. That along with a key injury to Brandon Carlo were major reasons why they did not get past the Islanders.

How much better equipped the second forward grouping is to succeed in playoff hockey remains to be seen. Krejci, a terrific player who had been a wonderful postseason performer with the Bruins, returned home to play in the Czech Republic. But the team’s best goalscorer, Pastrnak, is now part of the mix and Haula’s turnaround since being placed on the line on Jan. 1 has been remarkable.

New Year’s Day is the demarcation line in the Bruins’ season. That’s when Pastrnak, after years of success with Patrice Bergeron and Brad Marchand, was moved to the line with Hall. Haula, who had struggled in various roles in the first few months of the season, was given the first crack at centering the two star wingers. It was hardly a given that he would stick there. But he turned out to fit well and he’s gotten progressively better.

But Haula said the turning point for him was when he was made a healthy scratch on Nov. 28, a point in time when he’d yet to find a role.

“I think going back to when I sat out that one game, I was picking out a couple of things in my game where I wanted to focus on,” said Haula. “The defensive side of the puck was one of those things, moving my feet in the D-zone, whatever it was, just little things I started focusing on. I think that helped me, just taking little parts of the game and focusing on those instead of the big picture, that’s when things started going better.”

CASSIDY SAID HE is “still evaluating” who his starting goaltender will be for Game 1 of the playoffs, but he did say that Linus Ullmark will get the start on Thursday in the home finale against the Sabres and Jeremy Swayman will play in Toronto on Friday. Considering Ullmark will get the game when the Bruins’ regular lineup will be in play while Swayman will be playing in the regular-season finale against the Maple Leafs when the Bruins will most likely by giving rest to some regulars is a pretty good tell that Cassidy is leaning heavily toward Ullmark to start the playoffs.