BOSTON — Friday afternoon was not Kevin Garnett’s first time returning to Causeway Street as a member of the opposition. That homecoming came last season, and he was, of course, welcomed back with open arms.

It wasn’t even the first time Garnett had visited TD Garden this season; his Brooklyn Nets were in Boston for the regular-season opener.

His latest return, however, felt a little bit different. The Celtics team Garnett faced Friday was the first not to feature a single member of Boston’s 2008 championship squad.

The Celtics dealt their franchise player, Rajon Rondo, who came of age in the Garnett-Paul Pierce-Ray Allen era, to the Dallas Mavericks last week in a trade that sent shockwaves through the NBA. Seeing a C’s team without Rondo at the helm was a bizarre experience for his former teammate.

“Very weird,” Garnett said after the Nets’ 109-107 win. “I just saw (Celtics trainer) Ed Lacerte in the locker room and told him it was kind of bittersweet. Obviously, I’ve been contacting Rondo since just for his well-being, kind of staying in touch with all the guys. Obviously, we all stay in touch. I’m just glad everything worked out.”

Garnett said he was somewhat surprised to hear that Rondo had moved on from Boston but by no means shocked given the sheer number of high-profile names who have switched teams over the years.

“A little bit,” he said. “But nothing surprises me after Michael Jordan moved to different teams, (Shaquille O’Neal) moving to different teams, players in history going to different teams. I guess at that point, it’s just a matter of when and where.”

Garnett said all Rondo needs to do is “be himself” in Dallas, where he joined a team with far more weapons and exponentially higher championship aspirations than the one he left.

“Obviously, he has other players with a little more of a firm base, a little more of a championship base, around him, and I see him adapting to that with no problem,” Garnett said. “I was watching him play and I saw him getting up up on D like old times, he was talking, being himself. I expect great things out of him, and I wish him the best.”

As for the official breakup of the 2008 Celtics? Garnett’s certainly gotten an earful about it — a bombardment of “rest in peace” texts forced him to change his number, he joked — but he’s content with that squad’s place in history.

“We’re infinite,” he said. “Once you win once, you win forever.”