'Iron Man' star Robert had been set to play a small but pivotal in the tale of a female astronaut - to be played by Sandra Bullock - who must find her way back to Earth after her space station is hit by satellite debris but pulled out in mid -November.
Now George will play the astronaut who survives the space disaster with Sandra's character in the Alfonso Cuaron-directed project, according to The Hollywood Reporter.
The movie has been beset with casting issues for some time. Angelina Jolie passed up the leading role in the sci-fi film, despite being approached twice by bosses.
Although Natalie was reportedly first choice with the director, sources claim Sandra is popular with Warner Bros. executives as they feel the expensive effects will need a big name to justify the money spent.