Watch: Alfonso Cuaron Explains Why Robert Downey Jr. & Angelina Jolie Weren't Cast In 'Gravity'

Gravity, Angelina Jolie, Robert Downey Jr.The long, long journey for Alfonso Cuaron‘s "Gravity" wasn’t solely dedicated to the effects-heavy technical production. Before cameras rolled, the filmmaker went through an arduous process to nail down his leading actors. Way back in the spring of 2010, Robert Downey Jr. and Angelina Jolie were tentatively slated to lead the sci-fi thriller, but by the fall the actress had pulled out, setting off an arms race for the vacant role. Natalie PortmanMarion Cotillard, Carey Mulligan, Abbie Cornish, Rebecca Hall, Olivia Wilde and Blake Lively were all mentioned/considered for the part before Sandra Bullock signed on, with George Clooney joining the project at the end of 2010, replacing RDJ who had also exited. The rest is history, but what happened to the original duo?

Cuaron, who recently sat down with THR‘s Stephen Galloway, provided some info on the departure. "I thought I had written a small movie … just one character floating in space," Cuaron explained. "We started developing stuff [trying] to figure out the technology. And the luxury [was] that we could try many things. And part of that was conversations with actors. I had conversations with Angelina, but then she went to do one film, and then she was going to direct [‘Unbroken‘]. Something happens, you part ways."

As for RDJ, Cuaron didn’t want to pen the energy of the actor into a film that wouldn’t utilize his talents. "It became very clear that, as we started to nail the technology, or narrow the technology, that was going to be a big obstacle for his performance. I think Robert is fantastic if you give him the freedom to completely breathe and improvise and change stuff. [But] we tried one of these technologies and it was not compatible," Cuaron said. "And, after that, we [had a] week that we pretended as if nothing was happening and then we talked and said, ‘This is not going to work. This is tough.’"

Watch Cuaron’s talk below and let us know if you think "Gravity" would have been as good with Jolie and RDJ.