Minnesota coach Sam Mitchell said the 39-year-old Garnett will rest.
Garnett was a member of Boston's 2008 NBA champions, the first season after he was traded to the Celtics from the Timberwolves.
He has one year left on a two-year contract he signed with Minnesota this summer, but it could have been his final game in Boston.
Garnett joked with former teammate Brian Scalabrine, now a TV analyst for the Celtics, and a few other Boston employees for a while in the hallway when he walked into the building.
Mitchell said Garnett would have the night off with the team being on the second of a back-to-back after a victory in Brooklyn against the Nets Sunday.