McCarthy told his club's website: "If a player comes on loan, plays and feels he's developing then there's always a good chance of being able to keep them.
"He's a young lad who's well thought of at Old Trafford and he's a player Dave Bowman (Wolves chief scout) has known of for a long time.
"He's a mature player for his age and he's a Man United player in that he doesn't give the ball away. He's very conservative with his passing.
"Part of the thinking behind bringing him here was that he would be good cover for when Seyi Olofinjana goes away to play in the African Nations Cup in the New Year.
"So hopefully we can keep Darron here and he'll provide that."