Massa insists he will remain a "professional" racing driver in his own right at Williams.
According to Blick newspaper, Hulkenberg and his manager Werner Heinz are having "sleepless nights".
Lotus' budget is going to be boosted with Quantum money, Hulkenberg - is the next step.
Drivers mood differs after both appeared to be on the 2014 market.
The new line-up reflects Williams' determination to bring success back to the team.