Head coach Brad Stevens provided an update Sunday, per the team's Twitter account:
Thomas would end up starting the game and honored his sister with his shoes:
Thomas' sister, Chyna Thomas, was killed in a single-car accident Saturday.
The crash took place in Washington, but Thomas has remained with the team in Boston.
The Celtics hosted the Chicago Bulls in Game 1 of a best-of-seven first-round playoff series Sunday evening.
Thomas ranked third in the NBA during the regular season with 28.9 points per game and also led Boston in assists with 5.9 per game.