"It's still being worked on, but it's pretty much a done deal," a source confirms.

Rob Marshall is directing the movie adaptation of the hit Broadway musical in which Daniel Day-Lewis stars as an Italian filmmaker, Guido Contini, who is balancing his latest movie project with all the various women in his life.

On Monday, it was announced that Kate Hudson had joined the cast that already includes Nicole Kidman, Penélope Cruz, Marion Cotillard, Judi Dench and Sophia Loren.

While it's still not clear who the Black Eyed Peas frontwoman will be playing, the only big role still not cast as of earlier this week was Saraghina, a woman described as a "whore from Guido's youth."

But for all we know, Fergie, whose casting was first reported by Access Hollywood, could end up in a role we don't even know about. It happened with Hudson, whose part as a writer for Vogue working in Italy was created just for her for the flick.

Fergie, whose real name is Stacy Ann Ferguson, is a former child actress who appeared on television shows like Mr. Belvedere, Married With Children and Kids Incorporated. Most recently, she had minor roles in the movies Grindhouse and Poseidon.

Nine starts shooting in October in London.