The two PSL giants will lock horns in the quarter-finals of the Nedbank Cup at 18h00 today in a clash that will decide the team to face Tshakhuma Tsha Madzivhandila in the last four.
Mahlangu says the visitors can only hope to lose in extra-time or penalties so they can bow out of the tournament in dignity.
"Sundowns go into this one with 80 percent to 20 percent chances when you compare the two teams," Mahlangu tells snl24.com/kickoff.
"The dominance of Sundowns in terms of position can lead to them scoring more goals. If Pirates can only manage how to defend themselves well they've got a chance of bowing out with a draw in the penalties if possible.
"We wish to see the game go into extra-time and penalties because we want to see football at its best, providing us with a bonus. If they cannot defend well Pirates then Sundowns, definitely they are going to win. It's not easy to beat Sundowns because you cannot predict who they are going to field. That's what gives them an advantage.
"Pirates will definitely lose this one, but I just want to see them losing on penalties for them to show us that they have a pedigree of raising their performance against Sundowns, as they've been doing that all over the years.
"Do you remember the game where they burnt a stadium after being whipped too much? My wish is to see them go to extra time. The only chance of them winning is through penalties, but during full-time and extra-time they don't have a chance at all."