Coach Nick Nurse said the three core players -- all injured during a Dec. 18 victory at Detroit -- were able to practice more Friday.
Powell hurt his left shoulder, the same injury that caused him to miss 21 games last season. Gasol strained his left hamstring and Siakam injured his groin.
The Raptors have gone 6-5 since losing the three, holding down fourth place in the Eastern Conference. Toronto also has played the last two games without starting guard Fred VanVleet, who is recovering from a hamstring strain.
Powell's return should give the offense a boost. He is averaging 14.4 points and topped 20 points in three straight games before his injury.
Nurse said Sunday was ''a bit ambitious'' for Siakam and Gasol to return. There was still no timetable for VanVleet, who Nurse said is ''still immobile but making progress.''