UPDATE: Current rumor as of Friday morning is that Kara DioGuardi is also out, with Jennifer Lopez (firm) and Steven Tyer (tentative) joining the judging panel.

Ellen DeGeneres has announced on Twitter and her own website that she's leaving "American Idol" after one season as a judge. With Simon Cowell leaving too and Nigel Lythgoe reportedly returning as executive producer, this could add up to a major shakeup for "Idol," which has suffered a ratings decline in recent seasons. Fox is expected to announce a replacement for Cowell as early as Monday, the network's day to meet with the Television Critics Association.

Here's what DeGeneres said:

"A couple months ago, I let Fox and the "American Idol" producers know that this didn't feel like the right fit for me. I told them I wouldn't leave them in a bind and that I would hold off on doing anything until they were able to figure out where they wanted to take the panel next. It was a difficult decision to make, but my work schedule became more than I bargained for. I also realized this season that while I love discovering, supporting and nurturing young talent, it was hard for me to judge people and sometimes hurt their feelings. I loved the experience working on "Idol" and I am very grateful for the year I had. I am a huge fan of the show and will continue to be."

Fox and "Idol" issued these statements:

From Fox Entertainment chairman Peter Rice: "We love Ellen and understand and support her decision to bow out of Idol. We were fortunate to receive the humor, energy and love for talent that she brought to the show."

From Mike Darnell, Fox's president of alternative entertainment: "It was a joy to work with Ellen. She brought an incredible spirit to Idol and was a great new addition to the team. While we're saddened by her decision, we are very appreciative that she gave us ample notice so that we could work through it together."

From "American Idol" creator and executive producer Simon Fuller: "I loved Ellen's passion for the artists and her nurturing skills. She brought honesty and optimism to our judging panel and I will miss her greatly."