McCarthy, Bafana's record goal-scorer, bagged a late brace, including a stunning free-kick in a 2-1 last-eight success at Dobsonville Stadium, with Luvhengo Mungomeni netting first for Swallows.
Igesund said: "I think Benni was the difference. He was outstanding. He showed his class. He held the ball up nicely, shielded it well. He scored a wonder goal and all credit to him."
The semi-final draw for the competition takes place on Monday with Bucs, Golden Arrows, Bidvest Wits and Santos in the reckoning.