The Celtics will be without Jayson Tatum as Boston plays for its season in Saturday night’s Game 7 against the 76ers. He was surprisingly added to the Celtics’ injury report due to stiffness in his left knee and less than two hours before tip, ESPN’s Shams Charania reported that Tatum will be out with a left leg injury. Tatum returned late in the regular season after a torn right Achilles he suffered in last year’s Eastern Conference semifinals series against the Knicks. He made a triumphant return to the court in early March and averaged 21.8 points, 10.0 rebounds and 5.3 assists per game over 16 appearances in the regular season. Through Boston’s first-round series with Philadelphia, he’s put up 23.8 points along with 10.7 rebounds and 6.8 assists a night. Boston's Jayson Tatum is OUT for Game 7 tonight against the Philadelphia 76ers with a left leg injury. — Shams Charania (@ShamsCharania) May 2, 2026 It’s a brutal blow for the Celtics just ahead of the decider at TD Garden.…