A last-minute Sergio Aguero goal against QPR on the final day of the season gave the Etihad Stadium outfit a 3-2 win, and clinched top spot on goal difference.
Despite the last-gasp heroics, the Italian trainer feels that this time round the challenge will be more intense.
“We did a good job for the last two years and I hope we can do a better one in the next five,” Mancini told City’s official website.
“But we cannot rest or start thinking that because we won the title that we are the best.
“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 (Manchester) United and Chelsea will challenge us for the title,” he concluded.
By Gareth McKnight