The Australian forward, who is gearing up for his fourth finals, flopped during a four-month spell on his return to Millwall last season.
Despite a hero's homecoming, Cahill didn't start a game as he struggled to force his way into the Lions side.
But that has not put off Neil Harris as he looks to re-sign Cahill next term.
He said: “Tim will have a decision to make once the World Cup has finished. We'll have a conversation about his footballing future."