According to Blick newspaper, Hulkenberg and his manager Werner Heinz are having "sleepless nights".
Massa insists he will remain a "professional" racing driver in his own right at Williams.
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.