Grey's Anatomy and Private Practice show-runner Shonda Rhimes has said that she usually starts out knowing how she wants a season to end and then works in reverse.

With this season of Grey's, however, she has no clue how to wrap it up.

The reason is simple and boils down to business. With the original cast members' contracts set to expire in May, she's forced to play it by ear more than she might like.

“I don’t know what I’m going to do at the end of the season yet,” Rhimes says. “Until we know [who's coming back], we just don’t know [how the season will conclude]."

"So we’re taking it in a different way," she adds, meaning that she's looking at the upcoming season, the medical drama's eighth, as two separate seasons in a sense.

“We’re looking at it in segments,” she says. “We’re planning the first half of the season [now] and then I’ll plan the second half of the season when I know more stuff.”

Rhimes is sure Seattle Grace’s doors will be open beyond May 2012. She's just not sure who will walk through them. “I have no idea,” she hedges. “That’s not my job.”

Think any or all of the original stars will stick around? Would you still watch the show without Ellen Pompeo, Patrick Dempsey, Sandra Oh or Justin Chambers present?

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.