One of the Washington Capitals’ biggest concerns entering the playoffs was the Boston Bruins’ potent top two forward lines.

As it turned out, they should have been worried about everyone else.

Through the first three games of the teams’ quarterfinal matchup, five of the Bruins’ six goals have come from players not in their top-six offensive players. On Monday night at Verizon Center, the Bruins claimed a two-games-to-one series lead with goals by third-liner Brian Rolston, fourth-liner Daniel Paille and defenseman Zdeno Chara.

“That’s something we’ve been trying to prove all year — that we have that depth all around,” Paille said. “We’re not going to chip in every night but we’re going to chip in as much as we can.”

In Game 1, the winner was scored by Chris Kelly, the Bruins’ third-line center. In Game 2, Boston’s only goal came from Kelly’s linemate, Benoit Pouliot. In fact, the only top-six forward to score in the series has been Rich Peverley; he struck as the teams skated four on four in the second period Monday.

“It’s always been key,” Peverley said. “We’ve always thrived on that and it’s going to have to continue if want to keep winning.”

Getting secondary scoring has been out of necessity for Boston. The Capitals have done an impressive job shutting down the top two lines, the units most responsible for the Bruins finishing second in the regular season in goals per game with 3.17. Tyler Seguin, Patrice Bergeron, David Krejci and Milan Lucic all registered 60 or more points. In the playoffs, though, only Bergeron has a point — an assist on Chara’s third-period winner Monday. The other four leading scorers all have struggled to find the space they were afforded in the regular season.

On Monday, Bergeron’s line was matched up against Capitals defensemen Karl Alzner and John Carlson, while Krejci’s line was smothered by Roman Hamrlik and Mike Green.

Shutting out Seguin, Bergeron, Krejci and Lucic should work in Washington’s favor. And most times it would, except for the Bruins’ depth of scoring and what appears to be a weak link on the Capitals’ blue line. Both Paille’s and Rolston’s goals on Monday came with Dennis Wideman and Jeff Schultz on the ice.

After the game, Wideman and Schultz were tied for the league’s worst plus-minus at minus-4 apiece.

“It’s huge,” Rolston said of the third and fourth lines chipping in. “Depth is a big thing. The thing is the top two lines are playing against the best possible players on the other team. If you have depth of scoring, it plays a huge factor, for sure.”

With the third and fourth lines carrying Boston, it makes one wonder what might happen if the Bruins’ top scorers begin to make an impact.

“It takes everyone to win,” Shawn Thornton said. But “you need secondary scoring in the playoffs. We found that out the last few years.”