Sekotlong, who has five goals in the League, has been ruled out of the tie with a niggling groin problem. However, speedy Dutch attacker Orlando Smeekes is back in contention after recovering from a groin strain.
Meanwhile, United team manager Quinton Jetto expects Steve Komphela's men to be tested at Harry Gwala Stadium.
"I think for us it's a tough game, we are well aware of that and we know that we are going to have to fight and be at our very best to have a chance," he says.
"So we will give our all knowing that there is lot at stake, a chance to go to the final, something, obviously, we want to do."
He adds that Pirates possess quality all around the field.
"No, I think they are a quality team with quality players in every department so it's not gonna be easy for us but we will give it our best shot.
"We also want to finish the season on a high note. The players are all ready. We will go out focused to see if we can get a positive result."