"I'm delighted to get Andrew, I think we've got an exceptionally talented young player," he said.
"Someone has just asked me if we're benefiting from somebody else's problems. It might be seen that way and I would hate it if that was the case.
"I saw Andrew play three years ago in a friendly when I came here to Wolves, he was playing at Cheltenham for Southampton, and I marked him down then and we followed him and tracked him. Finally we've been able to sign him.
"I'm thrilled with it, he's a good player."
McCarthy continued: "I wasn't in a position to sign him three years ago, I would have had no chance three years ago when I came here. July 2006 - that would have been a non-starter.
"The really good scouts, which we've got, go out and mark players down, have a look back through their notes and remember what they've seen, and he's one that caught my eye.
"He caught everybody's eye as well."