McCarthy missed the last League game due to a calf injury while Manyisa has been out of action for almost two weeks with an elbow injury.
Pirates and United have faced each other in their last two games both ending goalless so goals are wanted tomorrow for either to qualify for the MTN8 Final.
Bucs coach Augutso Palacios says both players will have to have a medical assessment today to see if they will be able to play on Saturday.
"Both Andile Jali and (Thabo) Matlaba also suffered knocks during the League game against SuperSport on Wednesday.
"We will have to see at training if Benni (McCarthy) and Oupa Manyisa will be cleared to play in the game against SuperSport United on Saturday," says Palacios.
'Njenje' fielded a relatively new team against SuperSport in the last League game with regulars like Moeneeb Josephs and Daine Klate not playing.
Collins Mbesuma played in the absence of McCarthy and Palacios has appealed to club supporters to remain patient with 'Ntofontofo'.
"We gave some of our new signings like Masuku a chance to play against SuperSport. It’s never easy to play for a big team like Orlando Pirates and we need to give them a chance to adapt to our system and style of play.
"We need to be patient with Mbesuma. He is working very hard at training and I am confident that he will soon reach his best level in terms of his playing ability," he adds.