Following the 1-0 home defeat to Manchester City on Saturday, the Blues now find themselves sixth points behind both Manchester sides, who occupy the top two spots in the table.
However, Cahill points out that there is a long way to go in the season.
He said: "They are setting the pace at the top of the league at the moment, as are Manchester United. They're both getting very good results and scoring a lot of goals, but let's see.
"We're in September, so let's get to Christmas, January time - hopefully we'll be in and around the top and then we'll see from there. We're experienced in it, but it's disappointing to lose points here against Manchester City.
"We proved last season we've got enough to win the league, but we realise it's very difficult. We've done it twice since I've been here and both times it's been extremely difficult. Look at the strength of the teams around us, but it's just important that we fight to the end."