London - Pascal Wehrlein is a real alternative for Mercedes as early as 2017 should negotiations with Nico Rosberg falter.
That is the warning of team boss Toto Wolff, as it becomes increasingly clear that talks about extending Rosberg's stay at the German team could be fraught.
It is believed Rosberg, assisted by family friend Gerhard Berger, is pushing for a retainer much closer to the value of Lewis Hamilton's current deal.
'Know what we have'
Austrian Wolff told Sport Bild: "Right now, our goal is to continue with Nico.
"But if we do not come together, we have to think of something else."
READ: F1 rumour mill - Rosberg in talks with Ferrari?
Wolff suggested that although Rosberg has been driving impressively over the last seven or eight months, Mercedes is also in a strong bargaining position.
Wolff insisted: "We know that we have the strongest car, a very strong team and are well positioned for the future as well. That would be the main argument for Nico.
"We also know what we have in him."
Recruiting top drivers
The fact Mercedes has a theoretical free seat for 2017 will undoubtedly mean that top drivers like Fernando Alonso are potentially interested in filling it.
What if Ferrari's Sebastian Vettel also makes an enquiry?
Wolff answered: "I would tell him the same thing I've said to others in recent years. 'First, we are talking to our regular drivers. Only when we do not reach agreement, we can start to look around'."
Wolff also insisted that Mercedes has an in-house option for 2017 in the form of reserve driver Pascal Wehrlein, who this year was loaned out to Manor.
Wolff said: "Yes, absolutely. He has shown in DTM that he can win championships.
"At the moment he is in his apprenticeship at Manor and on the right track to being at Mercedes at some point."