The Brazilians are in second position on goal difference and a win against Saint George could cement their place in the next round.
Here's how the fans reacted to their big game on Wednesday night.
You can also watch the intimidating atmosphere at Rades in Tunisia, which received much criticism from South African fans due to how the smoke made visibility difficult.
Sundowns been traumatizing psl teams since inception, even before we've been at it , don't get it twisted Sundowns is a big team — Biko-ncious (@H_ezee) June 22, 2017
The notion that Sundowns supporters only declared their alliance to Sundowns after CAF is very lame — Biko-ncious (@H_ezee) June 22, 2017
Have u ever heard William Shongwe commenting objectively in a sundowns match? Funny how they justified Zwanes caution— LeHippy (@nkerelang) June 22, 2017