Speaking to News.co.au, Sibbett said:
I actually was up for another character. They wanted me to be one of the main six. It was actually Rachel but I usually don't tell people that because Jen... there's no one who could've done it like Jen.
Sibbett had to pass on the role as she was pregnant at the time. When she told this to the producers, they told her "it wouldn't work out".
But Sibbett says she has no regrets - "my goodness, there's no way anybody could have come close to what Jennifer Aniston did with Rachel. She was so perfect."
We gotta say, we definitely agree!