There was a short window, as free agency was about to begin on Sunday night, that it appeared Al Horford might be reconsidering his decision to leave the Celtics. He hadn’t scheduled meetings with any teams, and had maintained radio silence.

But according to a league source familiar with negotiations between the two sides, all of the drama prior to Horford’s decision to sign with Philadelphia, as well as much else about that night’s dramatic countdown, was staged.

“No, Al was never coming back to Boston — they had a deal done two weeks ago,” he said.

Horford’s agent, Jason Glushon, declined comment today.

Indeed, both of the Celtics’ celebrated departures and destinations had been completed well ahead of 6 p.m. Sunday.

“I do know there was some tampering across the league,” said the source. “Kyrie and Kevin Durant were done in Brooklyn months ago.”

Though the Celtics’ offer to Horford never came close to the four-year, $108 million agreement he reached with the Sixers, the source believes the 33-year-old center’s motivation for leaving Boston involved more than money.

Horford has always been uncomfortable in a traditional center’s role, and the nightly toll the pounding takes on his aging body. Though he guarded his new teammate, Joel Embiid, as well as anyone in the league, Horford may have also looked forward to a chance to finally be slotted as a pure stretch power forward. Had he remained in Boston, now with Aron Baynes gone, he likely would have seen more of the same.

“It was money, but also other factors,” said the source. “I think part of it was Al wanting to play with a true center. Joel Embiid is now the best center he doesn’t have to guard anymore.”