The Toffees have enjoyed a strong start to life under the Dutchman with four wins and a draw from their opening five league matches which sees them sitting second behind Manchester City.
But any discussion of Everton challenging for the premiership has been thrown out the window by Koeman who is simply focusing on improvement with the Goodison Park outfit.
"Normally, we can't win the title - I think what Leicester did last season was an exception," he said.
"I don't think so. I am realistic. If I tell you we will fight for the title I think most people will say 'that man is crazy'. Even when I mention that, I'm not crazy?
"Why do we need to change our mind about our aspiration and ambition after 13 points from five games?
"The big teams have much more qualities and if they are not disappointed like last season it will be impossible."