"I saw it was Toto (Wolff on the phone) and I thought 'Oh, again something with Lewis!" Mercedes CEO Dieter Zetsche told Autocar.
Actually, it was the news of Rosberg's retirement, and the fact Mercedes must now find a rapid-fire replacement.
"Of course, it would have been easier and more pleasant for us to have two world champions in our team for the season to come (but) that's how life works," Zetsche added.
Zetsche insisted he is not angry about Rosberg's decision, but it has left Mercedes trying to engineer a complex solution.
It is believed the eventual deal involves shortening Paddy Lowe's 'gardening leave' before he joins Williams, and paying big to break Valtteri Bottas' contract and help the Grove team convince Felipe Massa to return.
Bottas' manager Mika Hakkinen says it is a "dream scenario" for the Finnish driver, with the champion team having identified him as the best solution for 2017.
But Roger Benoit, a veteran F1 correspondent, said Williams and Bottas' management are demanding "lots of money" for it to happen.
"The billionaire father of F1 rookie Lance Stroll might be able to help financially," Benoit wrote in Blick. "Because his son might look better alongside Massa than Bottas."