The star attacking midfielder is being dogged by a knee problem and although he played in Saturday's 2-0 away win over Birmingham City is in some doubt to even travel down under.
Cahill, who scored the second goal to guide the Toffees to their first win of the season, missed two games earlier in the campaign with the injury and his manager David Moyes insist he is not fully fit.
''There was a doubt about Cahill today,'' he said. ''He is still not looking 100 per cent. He has not trained enough for me to think everything is absolutely right.''