Wydad came with the early pressure in the opening minute, but solid defending from Motjeka Madisha kept them from an early lead.
The South Africans responded swiftly with a close-range attack inspired by Gaston Sirino whose goal-ward run played in Anthony Laffor with a little dink, but the Liberian was unable to make contact.
A barrage of pressure from Wydad befell the Brazilians who struggled in great length to handle it effectively.
So much so that it needed offensive individuals such as Laffor having to track back and make defensive clearances in and around the 18-yard box.
All the while, the Tshwane outfit brought up pressure of their own with nice touches on the ball, but the killer aspect in front of goal let them down on this occasion.
The half-chances continued falling for Wydad, but good goalkeeping from Denis Onyango among other aspects continued denying them from going ahead after the half an hour mark.
A darting run down the wing from Laffor saw him skip past two defenders before playing in a cross, which the defence gathered well to clear for safety.
In the second half, Sundowns were forced to early defending again when Onyango charged off his line to make a crucial clearance to safety.
There would be no stopping a stunning strike from Anas El Asbahi from giving the hosts the lead, with the Sundowns shot-stopper given no chance on 56 minutes.
Downs threatened to pull back, but a snap shot from captain Hlompho Kekana did little to go past the opposite goalkeeper.
Following a double substitution in Jose Meza and Tiyani Mabunda, the Tshwane giants increased the tempo and became more offensive but lacked the proper ingredients to break down a Wydad wall.
On 65 minutes, Kekana made way for the new signing that announced his arrival with a goal against Polokwane City last week- Lebohang Maboe.
A shot from Meza from a free-kick situation went at goal with full venom but the opposite number came to the goods with an excellent save.
The defeat ensures a quarterfinal berth for the Moroccans, who are on course to defend their title, while Downs have it all to do in their final group game.
Sundowns: Onyango, Langerman, Nascimento, Ngcongca, Madisha, Kekana, Jali, Sirino, Zwane, Laffor, Vilakazi.
Subs: Mweene, Maboe, Arendse, Meza, Mabunda, Brockie, Zulu.