When a coach decides to give a player a healthy scratch, the hope is that it will light a fire under that player to get him to perform better.

Rarely does it work as well and as quickly as it did for Bruce Cassidy and Trent Frederic on Saturday. On Frederic’s first shift after getting scratched on Thursday, he won a puck race to keep a play alive, then bolted for the net and scored on the rebound of a Craig Smith shot just 49 seconds into the Bruins’ 2-1 win over the Pittsburgh Penguins.

It was exactly the kind of play that Cassidy had been looking, for not just from Frederic but the whole third line.

“Good for (Frederic),” said Cassidy. “Sometimes guys don’t respond well and then they come back and they’re bitter, or whatever word you want to use; Freddy wasn’t that way. It was explained to him why. And I thought he went out and practiced well (Friday) and got rewarded right away by going to the right spot. I like that Smith attacked the net. That line, as a I said the other day, was getting farther and farther away from the net. That’s what I mean. Smitty didn’t walk up any farther than he had to. He got good possession, collected the puck, saw a seam and got it to the net for a second chance. And that’s how they’re effective, that line, and we need more of that from them.”

It was Frederic’s sixth goal of the season, and he could have had his seventh in the second period, but he fanned on a good chance off the rush.

He had been scratched after taking a bad roughing penalty that helped sink the Bruins against the Blues on Tuesday. He got the message.

“I just wanted to play hard and help the team, play disciplined and obviously try to get a win. Any time they’re winning, that’s good,” said Frederic of the scratch. “Smitty made a good play, put it to the net. When our line’s successful, that’s what we do. I just got a good bounce and was lucky to put it in the net.”

Of his short time in the press box, Frederic said what many before him have said.

“It’s a lot easier up there,” said Frederic with a laugh. “You just see how much more time you have, you pick up on little things. I’m trying to watch the wingers now and seeing what other teams are doing. I think it helps any time you go up there. It happened to me in college where I hurt my hand and I had to watch for a month or so, and I thought it helped me then as well. We have a lot of good players, so it’s hard to be in this lineup every night.”

WITH DEFENSEMAN Brandon Carlo returning to the lineup, Josh Brown took a seat. The 6-foot-5, 217-pound Brown dropped the gloves on his first shift as a Bruin a couple of weeks ago, but Cassidy believes he can bring a little more nastiness to his game.

“Be a little more engaged in the game for what he brings. The other night, Ottawa had some big hits against us. One on (Taylor) Hall, maybe a counter hit on (Jesper) Froden. So we’ve got to respond with some physicality,” said Cassidy. “That doesn’t mean you go grab somebody. It’s just when you think it was a dirty hit – I think (Curtis Lazar) thought it was high on Hall. He responded and we want guys to stick up for each other. Not on every clean hit, but if we feel there’s one that might be a little across the line, whether it was right or wrong. I know the refs didn’t see it that way. At the end of the day, those are good responses for the team. And just maybe be a little more physical in front of our net in clearing out.

“They had some power-play opportunities, second chances, where you can send a message and put some of those younger guys on their (butt) in front of the net. Little things like that that, he’s able to bring better than a smaller guy. He had a couple of chances to clear pucks on the PK that I think he could have been stronger on. Just more urgency in his game. Sometimes it’s partner-oriented, too. I don’t know that he and (Derek Forbort) would be a great pair yet.”

Carlo, meanwhile, looked good in his return, logging 21:13 of ice time, finishing at plus-1 and helping the Bruins go 3 for 3 on the penalty kill.

With Frederic coming back, it was Tomas Nosek’s turn for a healthy scratch. Cassidy expects it to be a quick reset for Nosek, who hasn’t scored a goal since Jan. 2.

“(Nosek’s) game has slipped a little. He’s like some other guys. Tomas can give us a little more,” said Cassidy before the game. “We’ve moved him around, we like what he brings to the team. Freddy wasn’t going to be long term. That line has been excellent for us, just not as much recently. We addressed that. And (Marc) McLaughlin, he’s produced. We didn’t know how it would play out. We didn’t expect him to have three goals in six games. Good for him. He’s pushing guys.”

McLaughlin played just 7:21, including just three shifts in the third period. It was his fourth Garden game and first one without a goal. Nick Foligno saw just two shifts in the third.

HAMPUS LINDHOLM (knee) and David Pastrnak (core) remained out and Cassidy did not want to venture a guess on whether either would travel for a two-game road trip to St. Louis and Pittsburgh. But they’ve both been out almost two weeks and their timing is starting to be a concern.

“We’re not going to rush anybody, but they’re going in when they ready,” said Cassidy.