Jody Marks is confident South Manchester will mark their 65th anniversary by winning the treble.
Two goals from top scorer Adam Lavin helped them to a 3-2 comeback victory over Chigwell Athletic to extend their unbeaten run to 16 games.
Lavin sealed the win with a stunning solo effort to set up a trip to Norstar London Raiders A or Oakwood in the Peter Morrison Trophy and they are now just 90 minutes away from a trip to Wingate & Finchley.
"Missing five regulars from our starting XI, we showed great character to come back twice to win and move into the semis," said Marks.
"We made hard work of it, but we never expected an easy game and reaching the last four for the third year in a row is fantastic. With our full squad, we’re going to take some beating."
James Jaconelli had put Chigwell ahead after two minutes, but South took control after Lavin hauled them level on half-time. Chigwell regained the lead early in the second half when Ryan Cole capitalised on good build-up play involving Brad Gayer, Dean Ben Yosef and Steve Summers, but Marc Yaffe set up a grandstand finish with South’s second goal.
Then Lavin, with the ball sticking to his feet, turned three players inside out and buried it into the bottom corner to spark wild scenes on the South bench.
Chigwell’s misery was compounded when Craig Sandford was sent off after a second booking for diving in the area in the last minute.
Chigwell boss Richard Slater said: "Defeat was tough to take as we were ahead twice, but a five-minute loss of concentration means we’ve missed a semi-final place.
"Hats off to South Manchester — they battled well and just had the edge."
He described South’s second equaliser as "a disgrace", adding: "Sadly, we never got over that decision and we lost our focus which allowed them to score a great winner. We’re all gutted, but that’s life."