WALTHAM — Celtics president of basketball operations Danny Ainge regrets one thing about how the team’s draft night unfolded Thursday. But it was not related to a pick or a trade that fell through.

After the Celtics drafted California freshman Jaylen Brown with the third overall pick, team co-owner Wyc Grousbeck went out to the court to address the fans at the team’s TD Garden draft party, and he was booed. At that point, Ainge already had moved on to focusing on the Celtics’ next pick and there was little time to address a draft party. But he wished he had.

“The only thing I felt bad about that is that Wyc went out there,’’ Ainge said Friday. “If I would’ve known that, or if I wasn’t in the middle of something, I should have been the one that went out there and I would have been happy to and I would have enjoyed it. It’s what I love about Boston. When you’re throwing a no-hitter, they appreciate it, and when you get rocked in the second inning, they boo you. The only thing about that is I love the passion of Boston fans.’’

The cool reception Grousbeck received was probably more due to the Celtics once again failing to make a trade than it was frustration about the Brown pick. Regardless, the night had a lukewarm feel.

In addition to selecting Brown, Boston drafted French forward Guerschon Yabusele and Croatian Ante Zizic with their other first-round picks. Both could be stashed overseas.

Then the Celtics traded their first two second-round picks to the Grizzlies for a 2019 first-round choice. Boston also selected Notre Dame’s Demetrius Jackson, Providence’s Ben Bentil, and Iowa State’s Abdel Nader in the second round.

So a draft that seemed so full of possibility for Boston ultimately yielded just one player who is certain of being on the roster on opening night in the fall. In what has become something of a familiar refrain, Ainge made it clear that the lack of a franchise-altering move was not related to a lack of effort.

“We’ve been working really hard on trying to get a deal and do something significant, but we just haven’t been able to do it yet,’’ he said. And it’s not because we’re not trying, it’s not because we’re turning down or we overvalue our players or any of that stuff. It’s because you need a partner. I’ve said this many times before: I tried three years to get KG before we got him. It just takes the right time and the right place and have a partner that wants to do a deal.

“I want to do a deal. But it’s my job to oversee the Celtics and not do what makes me look really good and do something that’s instant gratification. It’s like we’re trying to build something. It’s a big responsibility and I take it very seriously.’’

On Friday, the focus began to shift away from what did not happen and more toward what did.

All of the new arrivals except for Jackson — who had a previous commitment and was unable to make it to Boston in time for the news conference — sat at a raised table on the team’s practice court and pulled on their Celtics caps while flanked by Ainge, coach Brad Stevens, and co-owner Steve Pagliuca.

Much of the focus, of course, turned to Brown. Ainge said the Celtics had been eyeing the 6-foot-7-inch forward for a couple years. He said he has seen so many basketball players over the years it is rare for any to make an extreme impression at first sight.

“But, yeah,’’ Ainge said, “he had me say, ‘Wow,’ a few times.’’

Brown, who averaged 14.6 points and 5.4 rebounds for Cal last season, completed two workouts in Boston, a 3-on-3 session that was followed by Monday’s individual work. Both meetings had an impact on Stevens.

“Very few guys can move like Jaylen, can move at his size and at his length,’’ he said. “So the defensive versatility is a big piece of that that should be transferrable right away. The other thing you see as you learn more about Jaylen, as you watch him more, is obviously the explosion, the work ethic.’’

Brown arrived in Boston on Friday afternoon with his mother and older brother. He seemed struck by the moment as he recited his appreciation for the Celtics’ history and tradition.

“My excitement level between 1 and 10, I’m about a 12 now,’’ Brown said. “I’m happy to be here and I’m gonna go to war for this city. I’m going to play with a lot of passion and leave it all on the floor every night.’’

Over the next week, the Celtics will begin to address the issue of what to do with these new players, because there certainly will not be room for all of them. There remains a strong possibility that Yabusele and Zizic will stay overseas and develop their games, with the Celtics retaining their rights.

Yabusele has been open to that idea over the past two days, but Zizic has made it clear his preference would be to stay in Boston.

“I think I’m ready right now,’’ he said, “so we’ll see.’’

Ainge said it was unclear whether the two Europeans would play for Boston’s summer league team. Stevens said second-year players Terry Rozier, Jordan Mickey, and R.J. Hunter and third-year wing James Young are expected to take part in summer league action, which begins in Salt Lake City on July 4.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.