The Blues sold Nemanja Matic to the Red Devils for £40m earlier this summer.
He got off to a blistering start with a classy performance in United's 4-0 demolition of West Ham at the weekend.
Chelsea, on the other hand, suffered a shock 3-2 defeat to Burnley and their squad looks paper thin.
And former Blues player and coach Wilkins is not optimistic about their chances this season following Matic's departure.
He told talkSPORT: "What an amazing impact that was yesterday from Nemanja Matic.
"I am a Chelsea supporter, I buy my season tickets at Chelsea, and I want to know whose educated decision that was to sell Nemanja Matic to Manchester United for £40m because it certainly wasn’t Antonio Conte's.
"As a Chelsea supporter, I want to know who made that decision.
"After winning the league with such a devastating midfield duo of [N'Golo] Kante and Nemanja Matic, why are selling one of them?
"Yesterday you saw what Matic can do.
"It could cost Chelsea the league and give the Reds the league."