The North-West outfit currently sit five points ahead of fierce competitors Manchester City, who dramatically snatched the title from United's clutches last season.
"Teams will drop points [in the title race]," Ferguson told the club's official website. "Not just us but Manchester City will drop points, absolutely, it's a certainty Chelsea and Arsenal will drop points.
"We'll probably drop two or three ourselves but the important thing is accepting the challenge that every game is just as difficult as the rest."
United take on Southampton this weekend.