City - who lifted their maiden Premier League crown under Mancini back in 2012 - sit third, 12 points adrift of leaders Chelsea, having dropped out of the UEFA Champions League in the round-of-16.

And despite acknowledging the differences between the Premier League and Europe's other top leagues, Mancini is surprised by City's failure to mount a serious title challenge this term.

"I was lucky enough to experience an exceptional period with City. We won so much and played great football," Mancini told the Sunday Post newspaper.

"Now they have Guardiola, who I consider a good coach. But they are struggling a little and there is a reason.

"In Spain, as coach of Barcelona, he had [Lionel] Messi, [Andres] Iniesta and a phenomenal team. Plus LaLiga is always a two-horse race with Real Madrid, the only rival.

"Then he went to Germany, where Bayern Munich always wins and therefore he did not have a difficult life.

"But, in England, it is a different story because you can have as many as six Premier League clubs who can vie for the title and now there are the problems.

"Still I am a little surprised because I think that from 2012, Manchester City is the strongest."