We are just weeks into the new Premier League season and already critics have been raving about the scintillating football of the two Manchester sides as opposed to the unimpressive form of Chelsea.
But apart from a disappointing goalless draw at Stoke on opening day, Villas-Boas' men still boast a perfect record and a victory at Old Trafford today would see them leapfrog the Red Devils in the table.
It is far too early in the season to make any serious judgment about Chelsea, who have been grinding out results at a steady pace without setting the world alight.
But all the signs are there for a resurgence and everyone who has already written off the Blues for the title would do well to pay attention to today's match.
Here are five reasons why Chelsea fans should remain positive and upbeat about the season ahead while City and United fans should keep looking over their shoulder.