Vilakazi has missed Sundowns' previous 10 matches in all competitions, Mabunda has sat out six games, while Arendse has skipped 11 fixtures due to injury.
"I can say Sbu is training now so Sbu will be back, and Mabunda is training, he could play but it's too early, he'll be back," said Mosimane.
"So we are waiting for Wayne Arendse. They'll come at the right time and this is the right time for the Champions League, which is very good."
Champions Downs today battle league title rivals Bidvest Wits at Bidvest Stadium (17h00).
Mosimane's side currently top the Absa Premiership standings with 50 points from 24 games, while the kings of Africa were recently drawn with AS Vita, Esperance and St George in Group C of the CAF Champions League.