I don’t know if director Alfonso Cuarón would consider Gravity a passion project, but it is certainly turning into a laborious attempt to get a film made. Just when it seemed like Cuarón had nailed a daring and capable actress to help get his $80 million 3D sci-fi film into orbit, Deadline reports that Natalie Portman has backed off. As we revealed last month, Portman was offered the role without having to screen test for it because of her critically praised performance in Darren Aronofsky’s Black Swan. Now Warner Bros. will have to turn towards another bankable actress in an effort to give Gravity some box office pull. Hit the jump for a string of possibilities and the leading lady they are eyeing.

UPDATE: Sandra Bullock has been offered the role, hit the jump for more.

update at bottom

Sandra Bullock was reportedly waiting “in the wings” if Portman didn’t accept the role, but nothing in Hollywood is certain these days. Remember, even Emma Stone can suddenly play Gwen Stacy instead of Mary Jane out of the blue. So now it becomes yet another waiting game for WB and Cuarón as they either reach out to Bullock or attempt to find another bankable replacement.

For those unaware, the film centers on “a female astronaut stranded on a space station after satellite debris slams into it and wipes out the rest of the crew.” While Robert Downey Jr. is already on board, his role is going to be minimal. The film has been repeatedly compared to Cast Away in how much the leading lady will be on screen, so in order for the film to be a success they need someone with more than just acting chops; they need a draw.

Deadline mentions a string of actresses that WB might turn to, including Naomi Watts, Marion Cotillard, Carey Mulligan, Scarlett Johansson, Sienna Miller, Abbie Cornish, Rebecca Hall, Olivia Wilde, and Blake Lively. However, none of these lead actresses are truly considered box office dynamite, which means Bullock might be the last chance this film has at getting off the ground and meeting the planned January shoot date. If your mind suddenly brings up the possibility of Angelina Jolie as a replacement, don’t bother; she’s passed on the film twice. As for Portman, she doesn’t appear to be headed off towards her own passion project, Pride and Prejudice and Zombies, as the film recently lost its director. Sound off in the comments for who you would like to see pulled into Gravity.

UPDATE: Right after reporting that WB and Cuarón are looking at Sandra Bullock to replace Natalie Portman, Variety is reporting that the offer is already on the table. This would truly be a great blessing for the film, as Bullock has shown she can headline a film and appeals to a wide audience. Warner Bros. knows this first-hand as The Blind Side smashed box offices last year with a domestic haul of $255,959,475 and earned Bullock an Oscar. Do you think Bullock is enough to pull you into Gravity? Sound off in the comments below.