According to Blick newspaper, Hulkenberg and his manager Werner Heinz are having "sleepless nights".
Vitaly Petrov could make a return to Formula One if indeed he has the sponsor with the cash that some teams just might need.
The numbers of available drivers for the Marussia F1 Team vacant seat continue to grow. Both Heikki Kovalainen and Vitaly Petrov were teammates with the Caterham team.
Berthold Bouman, F1 correspondent