Jayson Tatum, Jaylen Brown and the Celtics head into NBA title defense with something to prove

Boston Celtics Last season: 64-18, won NBA championship. COACH: Joe Mazzulla (third season, 121-43) SEASON OPENER: Oct. 22 vs. New York Knicks. DEPARTURES: G Svi Mykhailiuk, F Oshae Brissett ADDITIONS: G Baylor Scheierman, F...