Patrice Bergeron, Brad Marchand reunited, and Bruins on same page

The feisty Brad Marchand (63) has given the Bruins the upper hand in the past two games. Matthew J. Lee/Globe Staff

For most of four straight games, Claude Julien took a sure thing and threw it out the window. Desperation can do that to any coach.

There is no debate that Patrice Bergeron and Brad Marchand combine to form one of the NHL’s elite 200-foot tandems. The understated center and the loudmouth left wing have polar personalities. But when they play together, it’s like a bond between sodium and chlorine. The sum is greater than the parts.

Julien determined, however, that the team would be best served with Bergeron and Marchand playing on different lines. This started Nov. 8 against the Islanders and continued until Julien had seen enough during Tuesday’s 5-4 loss to San Jose.

Bergeron and Marchand have been back together for the last two games against Toronto and Minnesota. It may not be a coincidence that the Bruins won both times.

Julien wasn’t disappointed in the pair’s production. But he was not satisfied with the performance of third-liners Matt Beleskey, Ryan Spooner, and Jimmy Hayes. The line was neither possessing the puck nor creating chances at a level proportionate to their skill.

Julien had to stabilize the third line. He declared Marchand as the best player to do the job. So Marchand went down to play with Spooner and Hayes. Beleskey replaced Marchand alongside Bergeron and Brett Connolly.

Julien had a good idea what he was going to get from Marchand. He couldn’t say the same about Beleskey.

The ex-Duck is not a subtle player. The Bruins signed Beleskey to a five-year, $19 million contract to play a consistent, hard-hat, straight-line game. They did not project Beleskey to provide the peaks of Milan Lucic, the left wing he’d be replacing. But they also didn’t think Beleskey would be subject to as many valleys as Lucic experienced last year.

Beleskey’s start had been underwhelming. Julien tried him with David Krejci and David Pastrnak. The line didn’t do much. The Beleskey-Spooner-Hayes threesome wasn’t better. Through 11 games, Beleskey had two goals, two assists, and not much presence.

So when Julien switched left wings Nov. 8, he hoped Beleskey would elevate his game just as much he wanted Marchand to help Spooner and Hayes.

Beleskey, Bergeron, and Connolly helped keep John Tavares and Frans Nielsen, the Islanders’ top two pivots, off the scoresheet in the Bruins’ 2-1 win. One game later, Beleskey’s net-front jamming led to a Zdeno Chara goal in the Bruins’ 3-2 loss to Colorado. He had a helper on Bergeron’s game-opening goal in the 3-1 win over Detroit on Nov. 14.

But Bergeron’s line cratered against the Sharks. San Jose’s top line of Joe Pavelski, Joe Thornton, and Melker Karlsson chewed up Beleskey, Bergeron, and Connolly. They were on the ice for even-strength goals by Pavelski and Karlsson. In the third period, Julien reunited Marchand and Bergeron and replaced Connolly with Hayes. They have not been apart since.

Their chemistry showed before a first-period goal against Minnesota on Thursday. Christian Folin settled a puck in his own end and looked to make a D-to-D pass to Matt Dumba. But as the first forechecker, Bergeron took away the pass and forced Folin backward.

As Folin banked the puck off the end boards to his partner, Marchand launched into a full sprint. When Dumba flubbed his chip up the wall, Marchand was in position to seal off the outlet. Wild goaltender Devan Dubnyk stopped Connolly’s shot, but Marchand scored on the rebound.

On Saturday, Bergeron’s line excelled on defense. Julien rolled the threesome against Toronto’s first line of James van Riemsdyk, Nazem Kadri, and Leo Komarov. Toronto’s top three forwards failed to put a single puck on Tuukka Rask.

Returning Marchand to Bergeron’s flank worked. At the same time, Beleskey has played stoutly in both games. Against Minnesota, Beleskey started the game at full tilt. He attempted two shots, then fought Brett Bulmer off the draw after Marchand’s goal. It was his first scrap as a Bruin.

“We all want to be better than last game and bring that compete up in front of the home fans,” Beleskey said after the win. “We’ve got to get some wins here. If I could help by doing that, that’s what I was trying to do.”

Against Toronto, Beleskey played with Krejci and Loui Eriksson. In the third period, Beleskey’s puck control along the right-side wall drew two Toronto defenders. The Bruins made the Leafs pay for their coverage breakdown. Moments later, a wide-open Chara hummed a slapper through James Reimer for the winning goal.

The Bruins were in a good spot in their last two wins. The Wild were missing Zach Parise and Marco Scandella. The Leafs, playing on the second night of back-to-back games, do not have a deep roster. But it helped to have a sure thing in Marchand and Bergeron.

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The Bruins claimed Landon Ferraro on waivers from Detroit on Sunday. The 24-year-old wing is scoreless in 10 games while averaging 9:33 of ice time. The right-shot Ferraro, Detroit’s second-round pick in 2009, is a good skater and can kill penalties. He scored 27 goals and 15 assists in 70 games last year for Grand Rapids, Detroit’s AHL affiliate. He is the son of former Whaler Ray Ferraro.