Andre Villas-Boas makes his first visit to United as Blues boss having presided over a decent start to the campaign, which has yielded 10 points from a possible 12.
Yet that return has been completely eclipsed by the stellar form of both United and Manchester City, who both head into the weekend with 100% records and a massive advantage in goal difference.
Indeed, Wayne Rooney's eight Premier League goals are one more than the entire Chelsea squad have managed so far.
However, Fletcher feels United write Chelsea off at their peril.
Having been ignored so much, the Scotland skipper believes the Londoners will head north aiming to make a significant statement themselves.
"I think so," said Fletcher, when asked if a team so used to challenging for top honours could be piqued because they are being ignored.
"They started last season on fire and ultimately did not win the league, so you have to be careful.
"Chelsea are a top side, with a lot of experience. They have a new manager and have brought in some younger, fresher, exciting players.
"It is a tough Premier League. Although the two Manchester clubs have started particularly well, the other teams are going to be dangerous."
After making eight changes for the midweek trip to Benfica, the inclusion of Fletcher for only the second time since March amongst them, Ferguson is expected to revert back to the side which demolished Bolton at the Reebok Stadium.
David de Gea has already been promised a recall, whilst Anderson, Ashley Young, Nani and Javier Hernandez are amongst those likely to return.
Fletcher has no qualms about youth being given its head in such an important game.
"The young lads have been fantastic," said Fletcher.
"They have gained experience at different clubs so it is not as if they are new to Premier League football, but they have been like a breath of fresh air.
"The results speak for themselves. Long may it continue.
"It is going to be difficult for me to get back in the team.
"That is the challenge in front of me. I am looking forward to it."