Hayward, who scored 12 points on 5-for-13 shooting with four rebounds, three assists and four steals in 34 minutes, was trying to box out Sixers star Joel Embiid inside with about 3½ minutes to go in the fourth quarter when his right foot got twisted and he went down to the floor in a heap.
Boston eventually had to commit a take foul and then call a timeout with 3:08 remaining in the fourth to allow Hayward, who never got off the ground, to slowly limp along the sideline and directly back to Boston’s locker room.
This ankle is the opposite one from when Hayward suffered a gruesome leg and ankle injury in the opening minutes of his first game as a member of the Celtics in 2017, forcing him to miss the remainder of that season.
This season, Hayward bounced back to the form he showed before the injury as a member of the Utah Jazz, averaging 17.5 points, 6.7 rebounds and 4.1 assists while shooting 50% from the field and 38% from 3-point range.
Hayward has a player option on his contract for next season.
ESPN’s Tim Bontemps contributed to this report.