BOSTON — There was a very real sense of resignation in the Pittsburgh Penguins’ locker room late on Saturday afternoon at TD Garden.

They played hard against the Bruins. They fired 40 shots on net. They carried play for long stretches, notably in the first period.

The other team was just better. Much, much better.

A victory for the home team felt inevitable long before Saturday’s nationally televised matinee began and indeed it was as the Bruins, though not at their best on Saturday, had little trouble with the fading Penguins in a 5-1 victory.

While the Penguins played with considerable energy in this game, their attention to detail left their head coach frustrated.

One play in the second period left Mike Sullivan particularly miffed.

The Penguins were already trailing, 2-0, when what can only be described as a lazy and unaware line change gave the Bruins a three-on-two. Moments later, Brad Marchand beat Alex Nedeljkovic for his 399th career goal, effectively ending the game.

Lars Eller, Jesse Puljujarvi and Emil Bemstrom had been three forwards on the ice. They took their time heading to the bench and Sidney Crosby’s line was unable to get back into the play by the time Marchand scored.

3️⃣9️⃣9️⃣ FOR 6️⃣3️⃣❗️❗️❗️ pic.twitter.com/reP8g5GBvP

— Boston Bruins (@NHLBruins) March 9, 2024

“We’ve got to do a better job,” Sullivan said. “Our forwards change and give them a three-on-two. You simply can’t change. And if you’re tired, you simply can’t be tired. You’ve got to stay and compete. That’s what winning hockey is about. I thought we learned that lesson today.”

The Penguins don’t know much about winning hockey these days.

They’ve now lost five of their past six games. Dating back to the season-crushing third period in Calgary last week, the Penguins have been outscored 23-7.

Sullivan acknowledged that his team’s effort level was much better against the Bruins than two days earlier against the Capitals, when a Jake-Guentzel-is-about-to-be-traded coma paralyzed his team. This game was simply a matter of details, like bad line changes and painfully unnecessary penalties — hello Rickard Rakell, again — robbing the Penguins of any chance to be competitive against what is very clearly one of the NHL’s best teams.

Kris Letang quietly sat at his locker, expressing frustration about the bad line changes — there were others — and the Penguins’ defensive hiccups in a game when they had the puck for long portions.

Why all of the mental breakdowns?

“I don’t know,” Letang said quietly. “I can’t put a finger on it.”

Letang scored the Penguins’ only goal when it was 3-0 in the Bruins’ favor early in the third period.

Boston responded with a couple of more goals, eliminating any doubt of the verdict, as if there were any.

Up next for the Penguins? They get to chase around Connor McDavid and the Oilers on Sunday at PPG Paints Arena.

Edmonton has out-scored the Penguins 30-9 while winning all of its past five meetings.

Ten postgame observations

• Michael Bunting was a bright spot for the Penguins. While playing on Crosby’s left wing, he had a good look on his opening shift and was unable to covert on a breakaway during his second shift.

His speed was noticeable from the game’s outset.

“That’s my game,” Bunting said. “I thought I did some good things out there.”

It’s only one game and obviously, Bunting is going to require some time to get acclimated to his new surroundings. No, he’s not Guentzel. Not all players are. But he played well with the stars in Toronto and he’s got a track record of being a good player. Many seemed so disenchanted with the Guentzel trade that Bunting was largely spoken of as though he were some kind of second-class citizen.

Sure, he’s not Guentzel. But I’ve always thought he was a pretty good player and I like that he plays with a genuine edge. The Penguins are badly lacking that. Mixed with his speed, I think that edge will come in handy. He’s a great third wheel on a good line.

He was one of the Penguins’ better players on Saturday.

• Something isn’t right with Crosby right now.

Maybe he’s out of gas. Maybe he’s simply in a mini-slump. Maybe he’s upset about the team’s direction and it’s merely impacting his focus.

Yes, he did get an assist on Letang’s goal. He also failed to register a shot on goal on a day when the Penguins had 40. He was only credited with one shot attempt.

I don’t know that I’ve ever seen him more disengaged than I have during the past week. Something seems off with his game. It’s been a brilliant season for the captain but he’s not playing his best hockey right now. That’s putting it lightly.

• One of Crosby’s great accomplishments could be in jeopardy.

He has produced better than a point per game in each of his first 18 NHL seasons. Should he do it again this season, he will tie Wayne Gretzky’s record at 19 straight seasons.

Crosby currently has 64 points in 62 games, so he’s on pace but isn’t trending well. He has just one point in his past four games.

There aren’t many compelling reasons to watch the Penguins right now. Crosby’s pursuit of this streak is one of them and it will be interesting to see how he finishes the season.

Also, truthfully, I don’t really know that he cares that much about the record or his numbers. That’s never what has made him tick. Winning is what makes him tick, and that might explain his current funk.

• Nedeljkovic, in my view, should have stopped David Pastrnak’s goal, the one that started the scoring in the first period. Granted, he’s a great player and he’s armed with one of hockey’s best shots.

Still, even though a save there might have gone a long way, it’s very difficult to gauge the goaltending these days. Sullivan admitted as much.

“We aren’t setting them up to succeed,” he said.

No doubt about that.

• We will probably be seeing plenty of John Ludvig in the lineup following Chad Ruhwedel’s trade to the New York Rangers.

This is for the best. Ludvig is young and he needs to play.

He didn’t have a good day. Ludvig went for a big hit, which gave the Bruins an odd-man rush and ultimately led to their first goal.

Ludvig also had a trip to the penalty box and generally looked out of sorts all evening.

• This game could have been worse. Even though the Bruins were badly outshot in this game, they still won 5-1. And … they hit the crossbar four times.

This is a pretty telling indication of how many Grade-A chances the Penguins allowed. This has been an issue all season so you wouldn’t expect it to change against the mighty Bruins. It did not.

• I thought Eller was perhaps the Penguins’ best player in this game. He, too, hit the crossbar on a short-handed look and he did a lot of good things.

I’m shocked that there wasn’t more interest in him at the trade deadline.

• Kris Letang continues to struggle in a big, big way. He’s been so good all season but, like Crosby, seems completely out of it at the moment.

• What a team the Bruins are. Just a very, very impressive hockey team in every way. A well-oiled machine.

• The Oilers are in town on Sunday. They’re worth watching. They’ve also lost a couple in a row and probably won’t be in a good mood.

I wouldn’t be surprised if it gets ugly.

(Photo: Brian Fluharty / USA Today)