With four points from their opening three games, Al Ahly entered the game sitting second in the group, three points behind Sundowns.
The game was surrounded by a lot of drama hours before the whistle as Al Ahly's bus was met by hundreds of fans that didn't allow them to reach the stadium on time.
This prompted board members Mohamed Shawky and Hossam Ghaly as well as sporting director Sayed Abdelhafiz to file a complaint to the match supervisor.
On the pitch, the drama continued and the hosts were the more dominant side in the early minutes, but had to wait until the 23rd minute to take the lead.
A cross from Lyle Lakay on the left side was met with a one-touch finish by Peter Shalulile into mohamed el-shennawy's net.
Shalulile came close to completing his brace just a few minutes later after another cross from Lakay, but this time his effort went wide.
On the other side, Al Ahly couldn't create any clear-cut chance, and to make matters worse they were forced to take off Karim Fouad due to injury and he was replaced by taher mohamed Taher.
In the second half, Sundowns continued their dominance and if it wasn't for Mohamed El-Shennawy they could have scored more through Pavol Šafranko Domingo and Haashim Domingo.
Al Ahy had more of the ball in the latter stages of the game and their only dangerous chance came in the 83rd minute when Ali Maaloul sent an inch-perfect cross on Hossam Hassan's header, but the latter couldn't convert the ball towards the net.
Despite the defeat, Al Ahly still remain second in the group and now wins from their next two games, set to take place in Cairo, will ensure their qualification to the quarter-finals.