The 21-year-old Belgium international is under contract with the Blues until June 2017 and seen as one for the future.
He told BILD: "I know that I will have to return to Chelsea FC. They are convinced of my qualities.
"There will be no chance for Werder Bremen to snap me up or to extend the loan spell further.
"I am of the belief that I have everything needed to break through at a club the size of Chelsea FC. I am able to play good football even at such a club."