"Grey's Anatomy' stars Justin Chambers, Katherine Heigl, and "Grey's" and "Private Practice" star Kate Walsh open up to ET about their co-stars Emmy Award nominations, and about filming the new season without T.R. Knight.

Justin Chambers tells ET about co-stars Sandra Oh, and Chandra Wilson who recieved nominations in the Outstanding Supporting Actress category. Wilson also received a second nomination for Outstanding Lead Actress in a Mini-series or Movie for her role in 'Accidental Friendship.'

"She got nominated for two, it's exciting," he says about Wilson's nominations. "We're really happy for her, and for Sandra, and we're happy to be back at work."

The 'Grey's' stars also tell ET's Kevin Frazier what it's like filming the show now that T.R. Knight has left the cast.

"a piece of the puzzle is missing," Chambers says. "But you know, TR's going on to Broadway. "He's going to have a huge career ahead of him."

"It's really hard actually," Katherine Heigl adds about Knight's departure. "For me, he was such a source of friendship and support, and love and laughter. It doesn't feel the same."

ET caught up with the stars at the premiere of Heigl's film 'The Ugly Truth,' and Kate Walsh spilled secrets about what's in store for her character Dr. Addison Montgomery -- watch the video for more!