Thibodeau attends Celtics practice and film session ahead of opener

Tom Thibodeau, the former New York Knicks coach, attended a Boston Celtics practice on Monday and took part in a film session with coach Joe Mazzulla and stars including Jaylen Brown and Jayson Tatum, two days before Boston’s regular-season opener. Thibodeau, who was dismissed by the Knicks this summer after leading them to the Eastern Conference Finals, has appeared at several NBA team workouts this fall while remaining unsigned as a head coach.

Celtics players and staff described the visit as substantive. Jaylen Brown said Thibodeau broke down film from last season’s playoff series between New York and Boston and offered observations on how the Knicks exploited Boston’s personnel and tendencies. Joe Mazzulla called Thibodeau “one of the best coaches around” and said having him in the building “makes me better, makes our organization better.” Video circulated online showed Thibodeau speaking with coaches and players during practice; separate footage also captured him conversing with Oklahoma City Thunder general manager Sam Presti at a recent shootaround.

Thibodeau, 67, served as an assistant with the Celtics during their 2008 championship run and built a reputation as a...