BOSTON (AP) — Tuukka Rask knew how potent the Penguins offense was. He also knew he could shut them out.
‘‘Every game starts with zero,’’ the Bruins poised goalie said, ‘‘so you have a chance.’’
And two games ended with a zero for Pittsburgh as Boston completed a sweep with a 1-0 win on Friday night that sent it to its second Stanley Cup final, and maybe its second championship, in three years with a 4-0 series victory.
The Bruins will play the winner of the Western Conference finals. The Chicago Blackhawks lead the Los Angeles Kings 3-1 and can wrap it up Saturday night.
Rask’s second shutout of the Eastern Conference finals continued his domination of the highest scoring team in the NHL. The Penguins big offensive threats — Sidney Crosby, Evgeni Malkin, Jarome Iginla and James Neal — didn’t score a single point and Boston outscored Pittsburgh 12-2.
‘‘We knew we had to be at our best to beat this team,’’ Bruins coach Claude Julien said. ‘‘That’s exactly what happened.’’
Rask stopped 134 of 136 shots by a team that averaged 4.27 goals a game in its first two playoff series.
‘‘I don’t feel like they totally shut us down,’’ Crosby said. ‘‘I feel like we got chances, but Rask made some big saves.’’
The few rebounds Rask allowed throughout the series were quickly cleared away by a defenseman or a forward getting back into the play. On offense and defense, the Bruins always seemed to be in the right spot at the right time. They made precise passes and got their sticks in the way of many passes the Penguins tried.
In the clincher, all the Bruins needed was one goal and defenseman Adam McQuaid provided it with a 45-foot slap shot from the right that went over goalie Tomas Vokoun’s right arm at 5:01 of the third period.
Of Boston’s 50 playoff goals, 15 have been scored by defensemen.
‘‘I think first and foremost, we’re obviously trying to be solid defensively,’’ said McQuaid, who had one goal in 32 regular-season games but two in the playoffs. ‘‘It obviously feels good. It feels good to be able to contribute that way when you don’t normally.’’
Rask provided the final flourish when he gloved Iginla’s hard 40-foot shot as the final buzzer sounded.
Iginla had turned down a trade from Calgary to Boston before being dealt to Pittsburgh because he thought the Penguins had a better chance to win the Cup, but that turned out to be wrong.
The Penguins never led in the series.
‘‘I just didn’t play very well,’’ he said. ‘‘That’s when you want to play your best for the team.’’
McQuaid’s goal sparked a chant of ‘‘We want the Cup!’’ from the capacity crowd. At the end of the game, the Bruins were one step closer to another title.
They were outplayed for much of regulation in Game 3. But they improved after that and won 2-1 on Patrice Bergeron’s goal at 15:19 of the second overtime.
On Friday night, Boston’s Milan Lucic admitted, ‘‘We were a little sluggish the first two periods ... and we said, ‘We have to win a period to win a series.'’’
They did just that.
The top-seeded Penguins were trying to overcome both the disciplined defense of the fourth-seeded Bruins and history. Only three teams had lost a series after winning the first three games. The last was the Bruins in the 2010 Eastern Conference semifinals against the Philadelphia Flyers.
The Penguins felt they were ‘‘put together to win the Stanley Cup. That’s our expectation from Day One,’’ coach Dan Bylsma said. ‘‘You’re going to look at this as a missed opportunity.’’
Pittsburgh was swept for the first time in 47 series. The last team to do it to the Penguins was Boston in 1979.
The Penguins also lost the first three games of their opening-round series last year against Philadelphia before being eliminated in six games.
Rask, who replaced 2011 playoff MVP Tim Thomas when Thomas decided not to play after last season, was solid again with 26 saves, but didn’t have to stop many challenging shots.
‘‘He has been the reason why we’re here,’’ Bruins forward Patrice Bergeron said.
The Penguins had been shut out just twice in their previous 147 games before being blanked twice in the four games against the Bruins. Pittsburgh lost Game 1 at home 3-0.
Holding down Crosby and Malkin was the key.
‘‘He is the best player in the world,’’ Bergeron said of Crosby. ‘‘We did a good job with that.’’On the winning goal, Brad Marchand held the puck along the left boards in the offensive zone and waited for McQuaid to skate up ice. Marchand fed the puck toward the blue line where McQuaid, with no Penguins player close to him, unleashed the winning shot