Mercedes's engineering chief Aldo Costa has named in-house junior Pascal Wehrlein as a good candidate to replace retiring world champion Nico Rosberg.

Having digested Rosberg's shock news, the reigning champions want to appoint the German's successor within December, with names including Fernando Alonso being touted.

"I guess unfortunately for Mercedes, Fernando is not available," McLaren-Honda's new executive director Zak Brown told SBD Global.

Other contracted drivers are also in the frame, like Valtteri Bottas (Williams) and now Sergio Perez (Force India).

Lewis Hamilton, the continuing Mercedes driver, would appear to favour the appointment of an experienced driver.

"We will have a new car and so we need a driver with experience to help with development, which will be critical," the Briton is quoted as saying by Italy's La Repubblica.

Costa, speaking to Italian magazine Autosprint, admitted that team boss Toto Wolff's decision will be "very, very difficult", but he seems to favour appointing one of Mercedes's own junior drivers, Wehrlein or the Force India-contracted Esteban Ocon.

"We have developed heavily in young drivers to one day replace Lewis and Nico," he said.

"Clearly the opportunity has come a bit too early, but we believe that our young drivers have great potential.

"Pascal is the one with a little more experience, he has been developing the tyres with Pirelli for next year and could be one of the best choices."

However, he said that other options have still not been ruled out.

"The first choices are from our [junior] programme, the others depend on existing contracts. So we will have to put everything on a plate and make a pretty difficult decision at this time of the season," said Costa.

The 2017 season is scheduled to get underway on March 26, 2017.