Manchester City boss Roberto Mancini sees Chelsea as title challengers.
Mancini also mentioned Manchester United, but did not name Arsenal among their rivals.
He told City's website: "It is more difficult to win the title when you are defending champions. We start again as if from nothing; we must forget that we won the title. Every team will want to beat us and we must work harder than ever.
"I think there are four or five teams that can challenge but now, before the transfer window is closed, I think United and Chelsea will challenge us for the title."