The Citizens lost their second match of the campaign as they were defeated 2-1 by West Ham United at Upton Park, as defensive errors allowed Morgan Amalfitano and Diafra Sakho to fire the Hammers to the three points.
Redknapp wrote in the Daily Mail: "The way Man City are at the minute, you have to wonder if they'll go the same way as the last time they won the title. When Roberto Mancini won in 2012, they couldn't replicate it the next season, struggling in the Champions League and finishing 11 points behind Man United.
"If that was a bad defence to their title then, if City aren't careful, this one could be even worse. They are already in danger of going out of the Champions League and have four fewer points than they did at the same stage in 2012-13.
"You wonder if, having won the title the previous year, they don't show enough respect to some opposition. That certainly looked the case against West Ham on Saturday. That combined with some sloppy defending and individual errors must be worrying for them."
City are currently third in the Premier League, but they trail leaders Chelsea by six points after nine matches.