Lebohang Mokoena was the hero for the Brazilians, netting the only goal of the game midway through the first half.
Sundowns, missing a number of regulars, had the better of the first half, but were let down by some poor play in the final third.
Katlego Mphela shot straight at the keeper early on, while Siyanda Xulu had a goal ruled out shortly afterwards for offside.
But Mokoena did eventually get the goal Downs’ play deserved, reacting quickest after Oscar Ramogadi could only parry a powerful drive from Mabhuti Khenyeza.
Aces rung the changes at the start of the second half and it immediately paid off as they started asking some serious questions of the Brazilians’ defence.
Madoda Motha saw a towering header superbly saved by Brian Baloyi on 53 minutes, and continued to pile the pressure on for the remainder of the game. However, they could find no way past the solid Downs’ defence.