At the time, Chisholm, the managing director and co-founder of California-based Symphony Technology Group, never imagined that he was less than a year away from becoming such an integral part of this storied franchise’s future.

On Thursday, the Grousbeck family agreed to sell the team to an investment group led by Chisholm at a valuation of $6.1 billion. It is a record for a North American sports team, surpassing the $6.05 billion Josh Harris paid for the NFL’s Washington Commanders.

“I’m all about winning championships and raising banners, and doing that now, and also doing it over the long term,” Chisholm said in an interview with the Globe on Thursday. “I think [lead governor Wyc Grousbeck] has done an incredible job of balancing that, and I think that’s the path we’re on and that’s the path we should stay on.”

The sale is pending approval by the NBA Board of Governors. Fifty-one percent of the team will be sold to Chisholm soon after approval, with the balance closing in 2028. Grousbeck is expected to oversee team operations through the 2027-28 season.

A league source said that timeline will likely make the final price tag closer to $6.7 billion, because the shares sold in 2028 will be more highly valued because of the NBA’s expected revenue growth.

“Bill is spectacular,” Grousbeck told the Globe. “He checks every box as far as I’m concerned. He’s passionate about the team and he can make it happen. I feel that he really can be a great owner, and that’s what he burns to be. That’s his desire. He wants to be a great owner. He has all the tools and there’s a great fit here already with everybody he’s met.”

Within NBA circles, questions persisted about whether a new Celtics owner would agree to the setup that kept Grousbeck in control during this three-year period in which the Celtics are positioned to remain championship contenders.

But Chisholm made it clear Thursday that he welcomed the succession plan.

“When you look at the way the team has performed and the leadership that Wyc has shown around that, it’s kind of a no-brainer,” he said. “If you’re actually a fan and you’re passionate about winning, why would you change that? And that, to me, made it really a pretty easy decision.”

Grousbeck, meanwhile, said that although he will remain in charge for three more seasons, Chisholm will be actively involved in major team decisions.

“For 22 years it’s worked that I’ve been the governor in day-to-day control, but that also means being part of a partnership and consulting with the partners on major decisions: the budget, major trades, things of real import,” Grousbeck said. “So that’s going to continue absolutely over these three years with Bill, and I feel very comfortable that we’ve already built a partnership.”

The new ownership group also includes Boston business executives such as current Celtics co-owner Robert Hale; Bruce Beal Jr., president of Related Companies; and the global investment firm Sixth Street.

For months, Celtics co-owner Steve Pagliuca was the only person to publicly state his intentions to be part of the bidding process. But in recent weeks a group of finalists emerged that included Pagliuca, Chisholm, Philadelphia Phillies co-owner Stan Middleman, and The Friedkin Group.

Pagliuca was part of the initial investment group that purchased the team for $360 million in 2002. Since he already held a significant ownership stake and had developed such strong ties to the franchise, many industry experts viewed him as the favorite to be chosen as owner. Now, his tenure will likely end after this season.

According to a league source, Pagliuca’s final bid was slightly below Chisholm’s, but it was already fully financed.

“I would say it’s disappointing that our competitive bid didn’t prevail,” Pagliuca said by phone Thursday. “But if for any reason the current bid doesn’t go through, we’re still very interested. Now our total focus should be on trying to win banner 19, and doing whatever we can to do that.”

Pagliuca said that even after his time as co-owner is over, he will continue to “root hard” for Grousbeck and the Celtics. Grousbeck said he and Pagliuca exchanged “warm” private notes Thursday.

“The decision was made at a different level or a different place, but my personal feelings and my family’s feelings toward Steve will never change,” Grousbeck said. “He’s the legendary Pags to us and he’s been a great partner.”

Now, Grousbeck said, he is eager to begin this new partnership with Chisholm. Both are encouraged by the early connection.

Chisholm and his wife, who are both Dartmouth College graduates, attended the Celtics’ home game against the Spurs on Feb. 12 as Grousbeck’s guests, but the Chisholms sat across the court from Grousbeck and his wife, Emilia, to not draw attention to their connection.

Chisholm, who was born in Wellesley and raised in Georgetown, owns a home in Nantucket and said he intends to purchase a house in Boston soon. He plans to be at TD Garden when the Celtics return from their current road trip to play the Heat on April 2.

Grousbeck said that Chisholm spoke with president of basketball operations Brad Stevens “in depth” in recent days, and he was scheduled to talk with coach Joe Mazzulla on Thursday.

Chisholm said he is committed to maintaining the Celtics’ success, and he understands it will not be cheap. Next season, the Celtics’ combined salary and luxury-tax bills are expected to exceed $500 million, an NBA record.

“This team is incredible, the team they have right now, in every way,” Chisholm said. “But I think it’s even a bigger thing. I think you have to be from Boston to get it. This team, the legacy and commitment to excellence here, it is about this team, but it’s about forever.”

The Celtics lease TD Garden from Delaware North, the Jacobs family-led group that also owns the Bruins. There have been suggestions that a new owner could look to build a new arena for the Celtics.

When asked about that possibility Thursday, Chisholm said he had thoughts about the situation but deferred to Grousbeck, who pointed out that the current lease runs through the 2035-36 season.

“We’ll always do something together with [Delaware North], I would predict, and it’ll be renovating the Garden together with them overall, as we’ve done for many years together,” Grousbeck said. “We’ve each chipped into that. It’s really a partnership in that regard. That’s going to continue into the 2030s, and then we’ll probably both look and see what we should do.”

Adam Himmelsbach can be reached at [email protected]. Follow him @adamhimmelsbach.