However, Ballack believes his former club have the quality to beat City if they remain confident in their abilities.
The Blues legend told Goal: "I don't know if they can make 100 points every season, it seems difficult," he concluded. "Especially with the tight competition in the Premier League. Of course, this achievement shows the quality that City has. It is something that should challenge Chelsea and with the squad they have, they are able to do it.
"They are unbeaten right now in all competitions and they should develop a mental quality ahead of a game directly against Man City. That game could affect Man City as a team. In football a lot can happen, I wouldn't say Man City have won the title already.
"The new coach and the way they play, they are able to compete and they should maintain it and try to win it. Hopefully at Chelsea they don't think that Man City are too good! That would mean you give it up early. They are a strong opponent, of course, but they can be beaten."