Cahill could miss five games for the Toffees if he is called up for international duty for Australia for the Asia Cup in Qatar in January.
“Tim Cahill has trained this week. I’m worried about his knee and he’s one of those who is doubtful,” said Moyes.
“He’s due one game in Australia (against Paraguay) but we probably need to have a bit of a chat about it.
“I’ve got no problem with Tim playing for Australia, we’ve always been supportive of that. It’s a long way to go obviously.
“He goes and plays for his country and in fairness to Tim whenever he’s done that he’s always come back and played and has always put himself out there. He’s not someone who returns late from international duty.
“On this occasion, I don’t know whether he’s fit, that’s the big thing – but if he does have to go it’s only one game.
“The bigger thing is the Asia Cup because we could lose Tim to that in a similar way we lost Joseph Yobo and Yakubu to the African Nations so that’s a big issue. He could be called up in the middle of December and they’ve got that competition all through January.
“We’ve got to respect football in every part of the world, not just in our continent and you respect their FAs.”