BOSTON — It’s been a tough 18 months for Danny Ainge.

The last piece of the Boston Celtics’ 2008 championship team he built is gone, with Rajon Rondo traded to the Dallas Mavericks. After trading away Paul Pierce and Kevin Garnett two summers ago, Ainge held out hope he could hold onto the last of his franchise cornerstones.

In the end, he couldn’t, and while the Celtics’ president of basketball operations ultimately pulled the trigger, it wasn’t easy.

“You know, I know it’s a business in professional sports, but you really develop a lot of close relationships,” Ainge said Friday before the Celtics’ game against the Minnesota Timberwolves. “I loved watching Rajon. I loved visiting with him. Our 1-on-1 conversations were fun, entertaining, frustrating sometimes and always a surprise.”

Ainge and Rondo had talked about trade rumors — some legitimate, some not — in the past, but with the Mavericks deal developing over a matter of days, Ainge had not contacted Rondo during the course of negotiations. Thursday afternoon, as the Celtics and Mavs explored involving other teams in the deal, third-party leaks to the media convinced Ainge it was time to drop a line to his point guard.

Ainge called Rondo around 5 p.m. and asked him to come to the Celtics’ practice facility in Waltham, Mass. Rondo, being Rondo to the end, waited until 7:30 to drive in, saying he wanted to avoid traffic.

When Rondo did arrive, Ainge stressed the opportunity Rondo was going to, rather than the one from which he was being sent away. The Mavericks have the best offense in the NBA and should only improve with Rondo running point.

“I shared with him how much I appreciated what he’s done for us and how much I enjoyed our relationship and said I was rooting for him,” Ainge said. “Like Paul and KG when they were traded, they were going to what everybody thought was a special opportunity. Through I don’t think any fault of their own, it didn’t turn out like they hoped, but I think they were enthusiastic and excited.

“Rajon hasn’t gotten to that point yet, but I think he should be excited. I think he should be enthusiastic about the situation he’s going to. It makes me feel a little better. It is a great opportunity for him. I think he appreciates it, that he’s getting a chance to go to a terrific opportunity.”

Quite a few Celtics fans — or Bostonians masquerading as Celtics fans who have only watched a handful of basketball games in the last two years — bid good riddance to a point guard who could be as maddening as he could be brilliant. Ainge was far from gleeful in dealing Rondo away, though.

“The guy was a very unique person, but watching him grow and watching him develop as a man and as a person and as a basketball player, I enjoyed my interactions with him,” Ainge said. “So, yeah, it was an emotional time. We met (Thursday) night, and it was not an easy thing to do, but I believe it was the right thing to do.”

Thumbnail photo via Charles Krupa/Associated Press