Sidney Crosby still remembers walking through the tunnel at Ralph Wilson Stadium over 15 years ago, experiencing what Buffalo Bills players experienced every home game.

He still remembers the snow floating down on the temporary rink constructed on the field, where the Pittsburgh Penguins defeated the Buffalo Sabres on New Year’s Day. Still remembers the shirtless fans packing the stands, braving below-freezing temperatures. Still remembers the nervous energy and pioneering spirit that permeated throughout the first Winter Classic of the NHL.

“It was like this perfect mix between hockey being pure outside, combined with your dream of playing in the NHL,” Crosby told ESPN. “It was just so incredible. We’ve played in other ones, but nothing matches that feel coming out of Buffalo.”

The visionaries that pulled off that 2008 event helped make outdoor games a commonplace part of the NHL. The next Winter Classic is scheduled for Jan. 1, 2024, as the Seattle Kraken host the Vegas Golden Knights at T-Mobile Park. It will be the 15th Winter Classic and 39th regular-season outdoor game. There have been Heritage Classics in Canada, the Stadium Series across the U.S. and even a couple of games next to Lake Tahoe.

“I think the success of the Winter Classic was why the Stadium Series was established,” said Steve Mayer, the NHL’s senior executive vice president and chief content officer. “Go back to that time: The Winter Classic was on fire. Everyone was talking about it. There was an interest to do more.”

But what would have happened if the 2008 Winter Classic wasn’t a success? What would have happened if the game never happened at all?

“There were a lot of moments where, on the inside, you were holding your breath,” said former NHL COO John Collins, who worked for the league from 2006-15.

THE FIRST REGULAR-SEASON NHL outdoor game was the Heritage Classic hosted by the Edmonton Oilers at Commonwealth Stadium on Nov. 22, 2003.

It wasn’t without its logistical and operational issues, like the minus-2 degrees Fahrenheit game-time temperature that helped make the ice choppy and brittle. But the nostalgic high of seeing Oilers and Montreal Canadiens legends co-mingling, and NHL players recreating childhood pond hockey, overshadowed all of it. The Edmonton Journal said the event belonged in the same Canadian sports pantheon as the 1972 Summit Series between Russia and Canada.

The Heritage Classic offered some proof of concept about NHL outdoor games, to the tune of 57,167 frozen fans who turned out for the event.

“Hockey started in Canada. Playing outdoors was commonplace,” NHL commissioner Gary Bettman told NHL.com. “We could see the Heritage Classic as a common, unifying, bonding experience. We figured the colder the conditions, the stronger the bond.”

About a year after the Heritage Classic, NBC Sports executive vice president Jon Miller was watching the American League Championship Series between the Boston Red Sox and the New York Yankees when inspiration hit him.

NBC had signed a multiyear deal with the NHL earlier that year. The Heritage Classic showed outdoor hockey in the regular season could work. Why not piggyback on baseball’s best rivalry and have the Boston Bruins face the New York Rangers outdoors at Yankee Stadium?

Better yet: Why not have that spectacle scheduled for New Year’s Day?

While college football filled the schedules of competing networks on Jan. 1, NBC was counterprogramming with things like figure skating. By 2006, the network wasn’t scheduled to have any bowl games on Jan. 1 at all.

Sports fans were already watching television en masse on New Year’s Day. An outdoor hockey game, with two Original Six teams inside an historic venue, was bound to capture the attention of channel flippers.

Miller started figuring out if this was a solid idea or a pile of speculative slush. He asked Sam Flood, executive producer for NBC Sports, if this was “a realistic thing to do.” Flood gave him a vote of confidence, telling him that outdoor hockey “was the ultimate way to play the game.”

Miller brought the idea to NBC Sports chairman Dick Ebersol, who encouraged him to pitch it to Bettman.

Collins said concerns about a viable economic model had put future outdoor games on the back burner for the NHL Board of Governors, who met Miller’s idea with a lukewarm response.

“We needed to put an economic model around it, which allowed us to make the investment and create the event that we were trying to create,” he said.

It was a tricky time to talk economic models for risky events: The NHL was in the midst of a work stoppage that lasted over 10 months and caused the cancellation of the 2004-05 season.

After the league and the players had agreed on a new Collective Bargaining Agreement, Miller reengaged on the idea of a New Year’s Day outdoor game. By that time in 2006, Collins had joined the NHL from the NFL, and Miller found himself with an influential ally inside the league to change some minds. Collins and Miller reengaged with Bettman, who was an early supporter of the concept.

But to make the Winter Classic a reality, Collins also had to get his own house in order: The NHL didn’t have the kind of special events department needed to put on such an event.

“We had a lot of guys who know how to put on a hockey game. We needed guys who know how to put on a Super Bowl,” Collins said. “And that was kind of the group that we brought in.”

Once momentum started to build internally for the game, there were some important questions that needed answering.

Where was the game going to be held? Who would compete in it?

The Bruins were initially enthusiastic about playing a game at Yankee Stadium. The Rangers were less amped for it, thanks in part to Madison Square Garden’s complex lease agreement with New York. MSG has a property-tax exemption worth more than $40 million a year that would be violated if either the Rangers or the Knicks play any home games in New York City outside of their home arena. The Rangers would have been the road team against Boston in Yankee Stadium.

(The Rangers would eventually play as the road team in Yankee Stadium twice in 2014 and again at Citi Field in 2018.)

The venue proved to be the biggest obstacle. Yankee Stadium officials told NBC and the NHL they had no desire to reopen their building on Jan. 1 — and do the necessary prep work on a stadium that would be vacated in 2008.

Yankee Stadium was out, and soon after, so were the Bruins and Rangers … and almost every other team the organizers asked.

“NBC had a long wish list of teams that could host and then matchups and we just kept going down the list,” said Collins. “And it was ‘no, no, no, no, no, no.'”

Finally, the NHL got a “yes.” It was from Larry Quinn, the former managing partner of the Buffalo Sabres. “Larry was very forward thinking about a lot of things, as a business guy as well as a hockey guy. And so he raised his hand and said, ‘We’ll host,'” recalled Collins.

Ralph Wilson Stadium, home of the Buffalo Bills, seemed like the obvious site for the game. Collins used his NFL connections to secure it. But again, there were hurdles. Once Ralph Wilson Stadium was the venue, the NHL and NFL had to figure out logistics around the Bills potentially making the NFL playoffs.

“We had to come up with a plan where we could be ready with brand new field turf for the playoffs that would have started a week later,” Collins said. “The Bills weren’t expected to be in the playoffs, so it was a little easier.”

Luckily for the NHL — although not so much for Buffalo football fans — the Bills met those expectations and finished 7-9, outside of the AFC postseason. Still, the NHL was only able to start its build after Dec. 23, which was the final NFL game of the season at the stadium. That gave them half the time they had before the 2003 Heritage Classic to build the rink.

Now it was time to find an opponent for the Sabres, which proved even more difficult than finding a host for the game.

The NHL asked divisional and geographic rivals of the Sabres and received rejections each time. Finally, Collins heard back from David Morehouse, who had joined the Pittsburgh Penguins as CEO in 2007.

“He was also a pretty forward-thinking guy,” Collins said. “He said they could get their heads around that game. And obviously they had Sidney Crosby and Evgeni Malkin and were kind of an up-and-coming brand team. Suddenly, we had a matchup.”

Collins said there were other significant questions the organizers had to answer about putting on an outdoor game.

“Could we get a sponsor? Could we sell 80,000 tickets? And then there were operational concerns,” he said. “If the weather’s bad, what’s an official game? Is it like baseball? How many periods do we have to play? Two periods? We don’t have those rules. What if the wind is really bad? How do we adjust?”

Collins said that a working group that included himself, Bettman, NHL deputy commissioner Bill Daly, NHL senior vice president of hockey operations Colin Campbell and others began working though those various questions. The Buffalo Bills, meanwhile, were soothing concerns about the weather, ensuring the NHL that they had the staffing and the preparations to handle massive snowfall inside the stadium and its parking lots if necessary.

Through all the stops and starts, the obstacles and hurdles, the Winter Classic was about to become a reality.

THROUGH THE YEARS, the NHL has staged a New Year’s Eve celebration for Winter Classic staffers and VIPs that would feature the game’s intermission entertainers in concert — everyone from Billy Idol to the Goo Goo Dolls.

Collins remembers a much different scene on the eve of the inaugural game.

“I think Bill Daly and I shared New Year’s Eve together in the Adam’s Mark Hotel lobby, eating cold buffalo wings and drinking stale beer,” he said with a laugh.

The next morning, Collins was driving to Ralph Wilson Stadium when he saw the last thing that he wanted to see that day: rain drops.

Even the NHL’s best efforts can’t make ice playable through rainfall. In fact, one of the selling points for Seattle Kraken CEO Tod Leiweke in landing the Winter Classic was T-Mobile Park’s retractable roof, which can be partially closed to totally cover the rink in case of rain but keep that open-air feeling for the game.

Ralph Wilson Stadium offered no such protection.

“I remember driving in and I’m going, ‘Oh s—,'” said Collins. “But it didn’t rain. It snowed.”

The snow provided incredible aesthetics but considerable problems for players, both in visibility and in trying to pass the puck. The ice itself needed constant work. One area near the Sabres bench received attention a dozen times. Zambonis scraped the ice between periods and midway through the periods, creating delays in the game but making the conditions safer.

Collins credits Dan Craig, the NHL’s recently retired vice president of facilities operations, with doing what he could to make the game playable.

“Dan Craig kept the ice in … I don’t want to say ‘NHL quality shape,’ because it wasn’t. That first [game] was a little sketchy,” Collins said. “He ultimately made us invest in the technology to make sure that the ice is what it is today. He had to run out every period and patch the ice and stuff, which clearly kept the game going and no one got hurt.”

The ice wasn’t great. The fans were. Ralph Wilson Stadium wasn’t “The House That Ruth Built,” but any concerns about the atmosphere for the game were quickly eased when the organizers saw the crowd.

“That fan base treated it like it was any other big event. Like an AFC Championship Game,” he said. “It was like the same crowd. They were tailgating and had their shirts off and painted chests. It was amazing.”

The vibe was so compelling that it drew Bettman into the crowd, despite temperatures in the 20s and light snowfall. Collins recalls the commissioner saying that he didn’t want to be in the NHL suite for the first period, but wanted to sit with the fans to watch Winter Classic hockey.

“I give a lot of credit to Gary for having the guts to see the vision and support the vision, because I’m sure there was complaining from other parts of the [NHL],” Collins said. “There probably were some doubts that this was ultimately something that would turn out to be 37 sold out games. Not just a gimmick.”

There were those who thought it would be a gimmick, who were skeptical about the Winter Classic’s viability.

One of them was Sidney Crosby. “I mean, I didn’t see it playing out that way. I thought it might be just like a one-time deal,” he said.

But through the years, as a participant and a fan, Crosby knew the Winter Classic was here to stay.

“To see the way it went, and to see it continually get the attention that it gets and have the impact that it has? They’re fun,” he said. “But the first one was incredible.”