The Australian international has been in stellar form so far this season, netting nine goals and consistently providing a threat to opponents.
And ahead of the Boxing Day clash between the clubs, Blues boss McLeish has adulated Cahill, labeling him as a player to closely watch.
"He is fantastic. He is a player with a great standing spring and where defenders are just about ready to go up, he is already up there hanging and scoring goals galore," McLeish said.
"My players go into the game in fine fettle and there are no excuses. It is a tough game for us, we know Everton are a good side and on their home ground, very formidable."
The 16th-placed Blues take on the 14th-placed Toffees at Goodison Park on Sunday.