The three were in Southampton's youth team eight years ago and Walcott was the undisputed star.
Swansea ace Dyer said: "There was never any doubt Theo would make it big.
"I remember when I realised he was probably going to end up at Arsenal.
"We beat them 1-0 in an FA Youth Cup game, Theo got the winner, and everyone was talking about him.
"You could see Gareth had what it takes as well but it wasn't so obvious. He always had the technical ability - but he has sort of grown into that incredible pace and power he has now."