BOSTON (AP) — The Bruins defense shut down the potent Pittsburgh Penguins throughout the Eastern Conference finals. Then a Boston defenseman scored the goal that sealed the stunning sweep.

Adam McQuaid scored early in the third period, Tuukka Rask posted his second shutout of the series, and the Bruins reached the Stanley Cup finals with a 1-0 win on Friday night.

The Bruins dominated the series and held the high-scoring Penguins to just two goals. Pittsburgh never even had the lead in any of its four losses.

“I think first and foremost, we’re obviously trying to be solid defensively,” McQuaid said of the defensemen. “It obviously feels good. It feels good to be able to contribute that way when you don’t normally.

“You look at so many great efforts we had from guys. The last 10 minutes of the game, guys were all over the ice, doing whatever it took to preserve that goal.”

Boston will face either the Chicago Blackhawks or Los Angeles Kings when the Bruins shoot for their second Stanley Cup title in three years.

Chicago leads the Western Conference series 3-1 and can advance to the finals with a home win on Saturday night. If the Blackhawks get there, it will set up the first finals matchup of Original Six NHL franchises since 1979.

The Penguins’ season ended swiftly and shockingly as the league’s highest-scoring team got no points in the series from offensive stars Sidney Crosby and Evgeni Malkin.

“I don’t feel like they totally shut us down,” Crosby said. “I feel like we got chances, but Rask made some big saves.”

McQuaid scored at 5:01 of the final period on a 45-foot slap shot from the right over the glove of goalie Tomas Vokoun.

That unleashed loud chants of “We want the Cup!” from the capacity crowd.

“We were a little sluggish the first two periods,” Bruins forward Milan Lucic said, “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 was solid again with 26 saves, but didn’t have to stop many challenging shots. His last save came with his glove at the final buzzer on Jarome Iginla’s shot from 40 feet.

“He has been the reason why we’re here,” Bruins forward Patrice Bergeron said of Rask, who stopped 134 of 136 shots in the series. “We just played our game the whole time. We put a lot of pressure in their zone.”

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.