ST. LOUIS — Around 10 minutes before Penn State arrived at its first Frozen Four, smiling and high-fiving a gaggle of adoring fans on Thursday afternoon, the Boston University men’s hockey team showed up at the Enterprise Center for its 25th. They all wore suits, a lot of them black. Only a few interacted with any of the fans who lined the blue carpet, and only one  — the freshman goaltender who only got here three months ago — offered a grin worthy of the occasion.

In the 11 days leading up to the national semifinal, BU told everyone its expectation and its standard was to win a national championship. But just saying it doesn’t really matter, especially for an enigmatic group that hasn’t always tried as hard as it should. So when it was time to go, the Terriers arrived at the sport’s biggest stage and acted like they’d been there before, stone-faced as they confronted the hurdle they’d stumbled at each of the last two seasons.

When the puck finally dropped an hour-and-a-half late, an ultra-talented group that’s suffered through a season of drama, frustration and pessimism delivered a relatively mistake-free performance. And off to the national championship game they will go.

“After that [regional final victory] ended, not a single guy in this room thought we were losing this game coming up,” freshman defenseman Cole Hutson said. “That’s the energy you need.”

BU didn’t light the world on fire in its 3-1 victory over the Nittany Lions, but it entered as the better pound-for-pound hockey team and played like it. And really, that’s been most of the struggle this season. After each of BU’s many low points this year — the latest a disastrous loss to UConn in the Hockey East semifinal three weeks ago — head coach Jay Pandolfo pointed the finger at his own team. BU has proven it’s good enough to beat anybody — it’s a matter of whether or not the Terriers are interested in actually doing it.

BU would beat Penn State if it wanted to, and that’s why the group’s demeanor as they walked off the bus and into the arena was so important.

“We were ready from the jump,” Hutson said. “Our game plan was to win the game, not try to lose.”

Trailing 2-0 going into the third period, PSU made an inevitable late push to make things nervous, scoring 2:15 into the period and peppering BU goalie Mikhail Yegorov from there (the Nittany Lions recorded 18 shots on goal in the frame after entering it with 15). But even in that period, the Terriers found plenty of chances at the other end, before sophomore Jack Harvey scored the empty-netter to seal it with a minute to go.

Pandolfo didn’t seem too peeved about the third period, a sentiment he expressed at the postgame press conference and in his locker-room address to the team after the game.

“It’s hard,” he said, “to end a team’s season.”

After all, this was a game the Terriers won in the opening 40 minutes.

For all of the ways things could’ve gone wrong for BU on Thursday night, nearly everything went right in the first two periods. BU was not plagued by an inexplicable lack of energy in the first. It did not struggle to break out of its defensive zone, nor did it find much resistance as it glided through the neutral zone. Penn State did not jump on the Terriers like it did the Black Bears of Maine in the first round of this tournament. In fact, save for an odd-man rush here and there, the red hot Nittany Lions didn’t do much of anything, until their third-period push was too little, too late.

BU and its 14 NHL draft picks knew they would have the space and time to do what they wanted, and they took it against a Penn State team that was passive defensively.

“We watched a lot of video. We knew exactly what they were going to do,” freshman defenseman Sascha Boumedienne said. “So it wasn’t too hard.”

“We had an understanding of how they forecheck,” Pandolfo added. “We felt like we were going to be able to exit our zone pretty clean a lot of the time.”

BU was good in the offensive zone once it got there — specifically the second line of Harvey and seniors Jack Hughes and Matt Copponi — generating plenty of scoring chances on pretty passes to the slot. Perhaps, the Terriers will need to be a bit more pragmatic in the rock fight against Western Michigan that awaits them on Saturday, but they were dangerous in their sustained offensive zone time versus Penn State despite scoring both of their non-empty net goals in transition.

And besides, BU’s clean play in the offensive zone slowed down the pace of the game and prevented PSU from getting out on the rush, where the Nittany Lions and their top six forwards are so lethal.

“They’re a quick-rush team that scores a lot of goals on the rush,” junior forward Quinn Hutson said. “And I think we gave up maybe two or three odd-man rushes the whole game.”

Hughes put BU in front at 1:35 of the second period with his seventh of the season, pouncing on a botched save from PSU goalie Arseni Sergeev, who didn’t realize he dropped a wrister from Copponi. 

Nine minutes later, Hutson and fellow star freshman Cole Eiserman combined to put BU’s foot on Penn State’s throat, perfectly executing a two-on-one rush that ended with Eiserman blasting home his 24th goal of the season. Hutson skated all the way to the goal line before dumping it back to the Islanders’ draft pick for his 33rd assist.

“The kid honestly played it really well on the two-one-one,” Hutson said. “I was looking at the goalie the whole time and was itching to shoot it. But when you have a guy like Eiserman on the [one-timer] side, you can’t pass up on that.”

“Whenever 44 has the puck, I’m always expecting to get it,” Eiserman added. “He was just looking for an angle. He could’ve went around the net four times, he still could’ve found me.”

And that, when push comes to shove, is the talent this BU team possesses. Hutson will almost certainly win National Rookie of the Year on Friday, while Eiserman leads all freshmen in goals. It’s one of the reasons why, even though Pandolfo admitted on Wednesday there were moments this season his team “didn’t have a great feel” it would make it to St. Louis, he also said he “had plenty of belief in this group.”

“Because of the players that we have,” Pandolfo said.

After all, it’s never been a question of capability. And now, BU men’s hockey is one win away from its first national championship since 2009.