ST. LOUIS — The first crowd back at Busch Stadium in over a year was waiting all day for it. There was no other fitting way for the home opener to go, was there?

Arenado’s eighth-inning homer was his second as a member of the Cardinals, but his first in front of the 13,328 sellout crowd at Busch Stadium. This one propelled St. Louis to a 3-1 come-from-behind victory Thursday over the Brewers after getting carved up by Corbin Burnes for most of the afternoon. A hallmark moment for the organization’s newest — and brightest — player, and a hallmark moment for the already ceremonious day that was the return of fans and Opening Day ceremonies to the ballpark.

One game at Busch Stadium, one career curtain call. Simple math.

“No comparisons,” Arenado said. “This is one of the greatest moments.”

Eagerness for Arenado to enjoy the Busch Stadium experience began years ago, when he was a member of the Rockies and was told by Troy Tulowitzki to soak in how the Cardinals go about their business as an organization.

Acquired Feb. 1, Arenado’s fit on the club has been seamless from an organizational perspective in his first two months, but there have been some adjustments to be made — new colors, new digs, new rules, practices and preparations in a new city. For one, Arenado said that he had trouble getting into the home clubhouse Thursday morning.

But in recent days, he heard from another Cardinal who made the blockbuster move from Denver to St. Louis. Matt Holliday reminded him that he needs to soak in the Clydesdales, the red sport coat-clad Hall of Famers in the stadium, the first pitch from Scott Rolen, the fans — albeit in limited numbers to start the season. He also heard from other former Cardinals Jon Jay and Daniel Descalso, on top of current teammates, advice on how to be a Cardinal.

Those teammates needed to remind him in the haze of jubilation that he had to go to the top step to receive his curtain call.

“I know this town expects a lot,” Arenado said. “But you know, we expect a lot, too, out of ourselves.”

One teammate hasn’t thought that he needs much advice. 

Adam Wainwright, who went five innings in his sixth career home opener, recalled a recent night when he was watching “American Idol” with his kids. Arenado mistakenly sent a video of himself working on his swing to the entire Cardinals team chat.

It was meant for a coach, searching for feedback. It came in at around 7:30 p.m., long after a day of work.

“Our fans, I don’t know if they know this, but he’s so focused on being a world champion as a St. Louis Cardinals player. You can’t even believe it,” Wainwright said. “Guy eats, sleeps, drinks, reads baseball, and he wants to win as bad as anybody I’ve been around. He wants to win here.”

And Arenado does it while both elevating his teammates and learning from them in his own right. When Dylan Carlson made a remarkable run-saving catch in the first inning — saving Wainwright a handful of pitches to end the frame — Arenado’s intensity was as if he made the catch himself.

That intensity is what has made this marriage a seamless fit as well. Not that the aspect has been lacking, said manager Mike Shildt, “but it’s nice to add to it, and he definitely adds to it.”

“Our players have been like, ‘This guy is moving people’s needle,’” Shildt added. “This guy is moving my needle.”

That Arenado is doing so while slashing .345/.367/.586 with a hit in each of his first seven Cardinals games — making difficult plays appear blasé in real-time — simply adds to his example-setting.

On Saturday, two days after his first game as a Cardinal, Arenado admitted that he still wasn’t 100 percent comfortable with his new environment.

On Tuesday, he said that his new surroundings were becoming more second-nature.

On Thursday, he looked like he had been a Cardinal for years, giving the fans pining for in-person baseball a moment well worth the wait.

“Baseball, for me and a lot of people paying attention, is a magical game,” Shildt said. “We went to a magical place today.”