The Three Lions go into their World Cup qualifying double-header against Moldova and Ukraine with a lack of defensive experience, but Cahill is certain that Terry would never consider a U-turn.
"That decision has been made. He has moved on now," Cahill said in a press conference.
"I think that's done and dusted. That decision has been made and that's all history now. We know how well he did for his country and that's that."
Terry, a former captain of the national side, earned 78 caps for England.