Tatum (Achilles) is listed as out for Sunday's game against Orlando, Taylor Snow of the Celtics' official site reports.
Tatum will miss a second consecutive contest. However, with the Celtics locked into the No. 2 seed in the Eastern Conference, the team is getting ready for the postseason, likely meaning the entire starting lineup won't be available. Without Tatum on the floor, Jordan Walsh, who has started in Boston's last two games, is expected to remain with the first five.