PITTSBURGH — There stood Juraj Slafkovsky, seething over how his Montreal Canadiens choked away an early lead and surrendered momentum by coughing up puck after puck to allow the Pittsburgh Penguins five unanswered goals from the 14:37 mark of the first period through the 15:32 mark of the second period.

Don’t try to tell Slafkovsky that at least the Canadiens clawed their way back from a 5-1 deficit to earn a point in the standings before losing in overtime Saturday. He also wasn’t interested in taking the built-in excuse of this being a typical early-season game — the type we’ve seen all over the league this week following 14-day training camps replacing 24-day camps.

No, the 22-year-old wasn’t having it. He was rightfully pissed.

“Can’t let them do that,” Slafkovsky said. “We fell asleep, and I think it shouldn’t happen.”

Not one game into the season. Not ever.

“It’s our fifth year together,” said Slafkovsky, “and we kind of talk about it every single year…”

About how good starts to the season are built on urgency, attention to detail, and commitment to playing the right way when plenty of other teams are finding their way there through the first 10 contests.

The Canadiens kicked things off reasonably well with a win over Toronto on Tuesday before having two productive practices in Pittsburgh on Thursday and Friday. They came out gangbusters Saturday, got a goal less than four minutes in, took a 7-1 lead in shots, and knocked the Penguins completely onto their heels.

To help them right to their toes was, as Slafkovsky bluntly put it, “sh–.”

Lane Hutson also started his post-game scrum with an expletive, which he needlessly apologized for. Because the Canadiens need to be this hard on themselves to be who they believe they are.

If they’re going to meet the extremely high expectations they’ve earned for themselves, it’s going to be by holding themselves to the extremely high standards they set for themselves on their way to last spring’s Eastern Conference Final.

Well before they got there, the Canadiens habitually played loose and free in second periods, mismanaging the puck and complicating things in situations that called for efficiency and simplicity. They put themselves at a deficit going into the third period 28 times last season, and they had seemingly learned from that in avoiding doing it as frequently in the playoffs.

That’s what made Saturday’s reversal so disappointing to the players.

Canadiens coach Martin St. Louis wasn’t thrilled about it, either.

“In the second, you have tired bodies — especially our Ds — far from the bench, hard to change, and once the brain goes, it’s hard to prevent stuff,” he said. “That’s why you want to play much simpler in the second period, play a deeper game, and we got a little stubborn with that because we know what we can do in possession in the first (when) fresh, and in the third. It’s something we talk about.”

The coach said he’d like to talk less about it this season.

At least Hutson said St. Louis didn’t have to say much before the Canadiens came out for the third and scored three goals to salvage a point in the standings.

Captain Nick Suzuki, who put the Canadiens within reach with a goal at 18:46 of the second period, set up two six-on-five goals in the last two minutes of play.

Chris Kreider got one of them — his first as a Canadien, which came a little over 15 minutes after he set up Caufield’s second of the game — and Ivan Demidov got the other.

Hutson had assists on both after earning one on Suzuki’s goal, but he wasn’t talking about that after the game.

No, the 22-year-old was stuck on a giveaway he had in the eighth minute of the second period.

“It’s more of the same, for sure, and it’s a new season, and we want to kind of put that mistake in the past, and it’s kind of frustrating that it came back,” Hutson said. “I get a puck (with 13 minutes left in the second period), it’s a 2-1 game, and I could get it deep, and I try to make a play, and it kind of was a domino effect from there…”

Sam Girard made it 3-1 Penguins seconds later.

Then Tommy Novak and Ben Kindel scored within 91 seconds of each other to add insult to injury.

At least the Canadiens didn’t go back to the room licking their wounds.

“I’m confident that they’re managing that, too, in the locker room by themselves,” said St. Louis. “As coaches, we’re trying to do our job to steer them in the right direction, but at the end of the day, if your players don’t recognize that, I think you’re in trouble, and I don’t think that’s the case.”

Still, this team must find a way to break the habit while it’s happening, to stop a few bad plays from becoming too many bad plays.

And it’s not too early in the season to do it.

Never mind that players, teams, and even officials — the ones in this game missed a Demidov trip on Rickard Rakell before Kreider scored and then ignored Rakell breaking Demidov’s stick before Novak won the game in overtime — typically require more than a couple games to find their best selves.

“You’ve got a lot of teams that have good starts to the season, and we want to be one of those teams,” said Slakfovsky. “Second period like today can’t happen. We got the point, and that part is really good if you look at how we played in the second, but Tuesday’s only going to be harder…”

It’s going to be the home opener. It’s going to be against a Carolina Hurricanes team that crushed them in five games before winning the Stanley Cup. And it’s going to be a disaster for the Canadiens if they play as carelessly for 20 minutes of it as they did in Pittsburgh.