Sources: 'Today' staff shocked Katie Couric guest hosting 'Good Morning America,' going all out to win ratings week

Surprise rippled through the “Today” newsroom on the heels of this morning's announcement that former anchor Katie Couric would be anchoring with the enemy all next week.

“There were a lot of jaws dropping all over the place,” one staffer told us. “Then there was a lot of sniping.”

ABC announced on Thursday that Couric would be substituting for Good Morning America co-host Robin Roberts while Roberts is on vacation.

“Katie Couric is going to be sitting in this chair next to George Stephanopolis,” Roberts announced herself on the morning broadcast.

Couric followed up the announcement with her own tweet:

“Rise + shine! Excited to be back on morning TV next wk, guest hosting @GMA w/ @GStephanopoulos. #KatieOnGMA.”

Couric was the co-host of "Good Morning America" rival “Today” for 15 years before leaving the network in 2006 to anchor the evening news on CBS. She left that post when her contract expired in 2011 and is currently a special correspondent at ABC.

"Today" has long won the ratings war with "Good Morning America," but that gap has slowly been closing as “Today” experiments with new personality combinations on their morning couch.

Media analyst Brad Adgate tells Fox411 that he thinks Couric’s week at “Good Morning America” will bring about a spike in that show’s ratings and may even push it to beat "Today."

“I think Katie Couric on for one week will break the 'Today' show's consecutive string of 800 plus weeks as the top rated early morning show to an end,” Adgate said. “Early morning shows are personality driven since the programming is very similar. I think Meredith Viera was popular and some viewers have tuned out after she left the show. But I expect 'Today' show numbers to spike during the London Olympics this summer.” 



But Katie’s return to the morning isn’t the only thing plaguing “Today.” Rumors have swirled this week that “Today” co-anchor Ann Curry may be moved to another position within NBC News. New York magazine published a piece on "Today" host Matt Lauer that said: “[Matt] Lauer’s worth only increased when Meredith Vieira left and handed the co-anchor chair to Ann Curry, who in the eyes of many television-news executives has experienced a rocky transition to her new role.”

"Today" insiders told Fox411 that producers are anxious to win the ratings next week and have the staff on red alert to book guests that will keep viewers tuned into their broadcast.

“No one is going to get much rest this weekend,” one staffer told us.

The move also has some of Couric’s former colleagues questioning whether the former host wants to make a permanent return to morning television. But a source close to Couric revealed to Fox411 that filling in for Roberts is just a one-off and that Couric is focusing all of her attention on her talk show, “Katie,” which will debut in September.

NBC did not answer requests for comment.