TAMPA — The Lightning controlled the matchup Saturday, but the Bruins’ top line controlled the game.

Patrice Bergeron, David Pastrnak, and Brad Marchand combined for three goals and 11 points to lead Boston to a 6-2 victory in the opening game of the Eastern Conference semifinal series, with Game 2 set for Monday at 7 p.m.

But if Tampa Bay is unable to have a better showing from its shutdown line against the Bruins’ top line, while the Lightning dictate the matchups on home ice, it will have a hard time staying in this best-of-seven series.

In the opening round against the Devils, the Lightning’s matchup line of Brayden Point, Ondrej Palat, and Tyler Johnson along with defensemen Ryan McDonagh and Anton Stralman blanketed MVP favorite Taylor Hall. The same group was tasked with holding down the Bruins’ No. 1 line Saturday.

It did not go well.

“They’re a skilled group,’’ Johnson said. “They can have nothing and all of a sudden have that one opportunity and make you pay for it. We have to do a better job of being on our toes the entire time.’’

Point, the Lightning’s top defensive center this season, saw 12 minutes of even-strength time against Boston’s top line, yet was on the ice for all five of the Bruins’ even-strength goals. At least one member of Boston’s top line registered a point on each of those five goals.

“That’s how the playoffs work,’’ said McDonagh, a minus-3 on the afternoon. “You think it’s going all right and you are playing well then all they need is one look and one bounce to go their way and they can create. We said before this game, it’s all five guys on the ice, you have to be aware and play it all the way through your shift.’’

In the series victory against New Jersey, the line of Point, Johnson, and Palat combined for four goals and 10 points. But on Saturday, the trio had just one power-play assist and was a combined minus-12 while generating eight shots on goal, the same amount as Bergeron’s line.

“We have to do a better job and I know we can do that,’’ Johnson said. “It’s a challenge playing against them, and I know we can do that.’’

Lightning coach Jon Cooper would not commit to the same matchup in Monday’s Game 2. But one way or another, something has to change for Tampa Bay, no matter who is out on the ice against Boston’s top line.

“I can’t stress it enough of how you have to be aware of each and every member of that line and just be smarter with the decisions with the puck and compete extremely hard,’’ Lightning captain Steven Stamkos said. “Those guys are obviously very skilled but their competitive level is very high as well. Whoever is going to be tasked with them, whether we change next game or use Pointer’s line again, has to be aware because they are a very good line.’’