He accepts that Cahill's role in his teams has, at times, been difficult to accommodate.
"Can he be a centre forward? What exactly is he?," he says. "And that is why most of his career he has been better playing, if you play with three midfielders, one of three or behind a striker, rather than one of a midfield two.
"We have had to create a position for him, he has been the one who has stopped us at times playing two up top because we are not quite sure about him being an out and out central midfield player."