Van der Vaart has been impressed with City's performances this year - they beat Tottenham 5-1 at White Hart Lane in August - although he does think the wheels could come off their title assault at any point due to the big egos in the City dressing room.
"At the moment they are really good. They are winning games easily and how they played against Man United was impressive, but they also have the difficulty of a lot of egos so that could also be a problem," the 28-year-old said.
"When you play for a big team, when they buy a lot of good players and a lot of players also aren't happy.
"Look at (Emmanuel) Adebayor. He is a great player for us, but he was not even in the squad at City and was training with the youngsters."