I think this season is showing how difficult it is to revamp a winning team and maintain the same level of performance/drive.
Liverpool's new signings plus an aging midfield has affected them. City are struggling a match the insane consistency they have shown over the last 5 years.
Arsenal is fresh and loving the moment they are in...same can be said for United all be it 12 months behind the curve Arsenal are on.
Arsenal are playing without any fear/pressure at the moment, so its up to the clubs chasing them to add that pressure by getting closer. United have that chance this week...lets see what the table looks like on Monday morning.