A trade that could wind up haunting the Toronto Maple Leafs for years only took about an hour to consummate.

Brad Treliving didn’t formally engage with Boston Bruins counterpart Don Sweeney on defenseman Brandon Carlo until around 2 p.m. ET at the 2025 trade deadline, according to multiple league sources familiar with the talks. The general managers had previously discussed general parameters of a potential Carlo deal, but it was only with the clock ticking loudly that they finalized the most important details included in a relatively complex deadline-day deal.

One year later, those details all appear to have swung decidedly in the Bruins’ favor.

Start with the fact that Fraser Minten, the coveted young player Sweeney landed in the deal, will line up as Boston’s top-line center when the teams face one another at TD Garden on Tuesday night. Then consider that Toronto currently has the NHL’s sixth-worst points percentage with a little more than three weeks left in the regular season, a shocking decline made worse because Boston owns the rights to its first-round draft pick in June provided it falls outside the top five selections. That was the other major piece the Bruins secured in the March 7, 2025 deal.

It was a serious swing (and miss) the Leafs front office never would have taken if it had any idea how dramatically the team’s fortunes were about to turn.

That it will end up benefiting an Atlantic Division rival, much less the Bruins — who have won four straight playoff series over Toronto since 2013 and previously snagged Tuukka Rask and the draft picks that became Tyler Seguin and Dougie Hamilton in trades with the Leafs — only makes it hurt more.

A critical point to highlight when looking back at why the Leafs wound up making the Carlo deal is that they were on their way to a first-place finish when the 2025 trade deadline arrived. With a ninth straight postseason berth at hand, they were all-in on a Stanley Cup chase.

The team’s front office worked that deadline period from a small conference room at the Ritz-Carlton in downtown Denver. They had a lot of different balls in the air. Not only had they identified the acquisition of a right-shot defenseman and third-line center as top priorities, they were also working through possible trade scenarios involving Mitch Marner, who ultimately refused to waive his no-movement clause.

The Leafs’ primary target for an upgrade on the blue line was Calgary Flames defenseman Rasmus Andersson, according to league sources. However, those discussions broke off March 6 — a day before the deadline — when the Flames backed away from the table. Toronto’s front office then spent that evening focused on superstar winger Mikko Rantanen, who wound up being dealt instead to the Dallas Stars by the Carolina Hurricanes, which left Leafs management still with two key holes to fill when they got back to work before sunrise the following morning.

First came the trade that landed them center Scott Laughton from the Philadelphia Flyers. They paid a premium to get that done, with a top-10 protected 2027 first-round pick and prospect Nikita Grebenkin — a return they couldn’t recoup when Laughton was flipped to the Los Angeles Kings for a conditional third-round pick earlier this month.

The market of available defensemen had grown thin with Andersson out of the mix. There was some consideration given to bringing back Luke Schenn for a third tour of duty in Toronto, but management felt the cost was prohibitive. The Flyers had set an even higher price on Rasmus Ristolainen, another potential option to fill Toronto’s need for a defensive stopper on the right side.

After exhausting their options, the Leafs zeroed in on Carlo — and needed every available second before the 3 p.m. ET deadline to land him. In a video later released by the Leafs, it was apparent that they narrowly got the Carlo trade details into NHL Central Registry before the window closed.

Former Leafs president Brendan Shanahan was shown anxiously imploring Treliving: “Is it in? Do we have it?”

Treliving replied, “Yes. Done.”

Acquiring Carlo amid a 108-point season was a perfectly sensible thing for the Leafs to do at that moment. He arrived with 72 games of playoff experience at age 28 and was signed to a reasonable contract through 2026-27, with the Bruins agreeing to further reduce his cap hit to $3.485-million by retaining 15 percent of the deal. The Athletic awarded the Leafs a B-plus grade in real time.

With the benefit of hindsight, it would now receive a failing mark.

Carlo hasn’t been the defensive stopper the Leafs thought they were getting and last year’s playoff run stalled out in Game 7 of the second round against the Florida Panthers. Then the team took its precipitous fall down that standings in 2025-26, turning the deal into a cautionary tale for any future deadline buyer because management didn’t adequately protect the downside risk.

There aren’t many other examples of NHL teams only securing top-5 protection on a traded first-round pick in recent years. And when that same condition was included in the March 2023 Jakub Chychrun deal between Ottawa and Arizona, for example, the Senators were only six weeks from the end of the regular season their pick was tied to, not a full year out like Toronto.

It also represented a change in course from how the Leafs had previously done business, after they secured top-10 protection on the 2020 first-rounder they sent to the Carolina Hurricanes to get rid of Patrick Marleau’s contract, plus the 2025 first-rounder they sent to the Chicago Blackhawks for Jake McCabe and Sam Lafferty.

Even the Laughton pick dealt hours before the Carlo trade was top-10 protected.

Asked earlier this month why the Leafs ended up with only top-5 protection in the deal with Boston, Treliving told reporters: “Because that’s what we had to do to get the deal done last year.”

How hard did you push for better terms?

“We pushed,” he replied.

From the Bruins’ end of the equation, landing Minten in the trade was seen as the biggest victory in real time, according to league sources. They had been impressed with the young center ahead of the 2022 draft, but didn’t select until No. 54 that year and saw Minten go off the board at No. 38 to the Leafs.

Everything they subsequently heard about his attitude and drive to improve during diligence calls made last winter helped reinforce their belief that he could one day develop into a second-line center at the NHL level, eventually able to replace Charlie Coyle’s minutes as he was being shipped out to the Colorado Avalanche in a separate transaction.

While Minten had plenty of fans inside the Leafs front office, too — Treliving told reporters, “You can’t say enough about Fraser; he’s just a wonderful young man,” after completing the deal — there were some voices inside the organization who felt his ceiling would see him top out as a bottom-six center.

The early returns are in Boston’s favor.

Minten was named January’s NHL rookie of the month and injuries to Pavel Zacha and Elias Lindholm before the Olympics saw him temporarily assume a role inside Boston’s top six while producing stout defensive results. He’s currently skating between Marat Khusnutdinov and David Pastrnak.

Minten’s 31 points in 70 games would rank seventh among Leafs forwards this season.

After the 2025 trade deadline passed, Sweeney characterized it as an “aggressive market” and applauded rival teams for going all-in to bolster their chances. He only elected to trade Carlo because the action wound up being so frothy.

“Every one of these decisions have been difficult,” he said. “(The departing Bruins players are) going to teams that we are jealous of. We’ve been in the same situations with those teams, they’re loading up. Had we done our jobs — if I had done my job appropriately, starting there — we would be adding like we have in 10 previous years.”

Now back inside the Eastern Conference playoff picture, holding down the first wild-card position with 12 games left on their schedule entering play Tuesday, the sting from the tough decisions in 2025 has long since worn off.

The feelings around the Minten/Carlo deal are a big reason for that.

“It was a steal for us,” Bruins coach Marco Sturm said recently.