Rachel who? Jennifer Aniston stars in the upcoming drama Cake, appearing like you've never seen her before. 

A new trailer for the feature debuted on Good Morning America on Tuesday, Nov. 25, showing viewers why the actress is already receiving Oscar buzz for her starring role. 

Due out in January 2015, Cake features Aniston, 45, as a woman named Claire Simmons, who is struggling with overwhelming chronic pain. Claire's life takes a turn when a fellow pain sufferer from her support group named Nina (played by Anna Kendrick) commits suicide. 

Claire becomes obsessed with Nina's life and death, and gets to know the deceased woman's husband Roy (Sam Worthington) in the process. She faces her own demons and struggles, attempting to treat her pain through a variety of methods.

The latest preview opens with an almost unrecognizable Aniston, with her makeup-free face filled out and her normally immaculate honey blonde locks in a messy, cropped, brunette bob. She is shown picking up pills from a pharmacy, having consultations with doctors, and speaking about Nina's death in her support group.

The transformed star goes gritty, with her character Claire talking about suicide and evaluating her own dark life. The buzzed-about flick also stars Chris Messina, Felicity Huffman, William H. Macy, and Adriana Barraza, among others. 

Aniston has been outspoken about the departure she took for Cake. "I basically just didn't work out for two-and-a-half months," she said in a Q&A for the movie last week. "I stopped working out and I stopped being as careful about my diet as I normally am. I was still healthy, but I'd allow more."

The stunning actress also went entirely without makeup for the role, a move she called "dreamy and empowering and liberating." Read Aniston's thoughts on the role. 

Watch Aniston's award-worthy turn in the video above!