The 32-year-old Ivorian spent four years at the Etihad Stadium before moving to Anfield in May on a free transfer.
Following a string of impressive performances for the Merseysiders, Toure believes that City are "kicking themselves" for letting him go.
"I was better than certain players at Manchester City but I was left on the bench," he told The Sun.
"Before I left the club, I told the people in charge that they would regret letting me go. People said I was finished and that I could never get back to my former level.
"But now I am at Liverpool - and I am sure that City must be kicking themselves when they see how I am performing."
Toure has made 11 appearances in all competitions for Liverpool so far this season.