Asked recently if - in the interests of continuity - Romain Grosjean will definitely be retained next year if Kimi Raikkonen departs, team boss Eric Boullier answered simply: "Yes."
So that leaves only the cockpit currently occupied by the Ferrari-bound Finn Raikkonen to fill.
The candidates are Hulkenberg - the impressive German who after moving from Force India last year is now seeking to jump from struggling Sauber - and the experienced Ferrari refugee Massa.
Brazilian Massa, 32, might have the edge.
According to O Estado de S.Paulo newspaper, Frenchman Boullier said recently that, "In 2014, experience will be more important than speed".
He is referring to the move from the current engine rules to next year's regulations surrounding the turbo V6s, which according to most of the sport's technical insiders is perhaps the biggest shift in the history of F1.
That is why, on the face of it, while the younger but hugely promising Hulkenberg perhaps should be the favourite, Massa's vast wealth of experience might have him in pole position for the seat.
A source close to Boullier told Brazilian correspondent Livio Oricchio: "The chances are 50 per cent apiece for Hulkenberg and Massa."
Oricchio said the prize on offer is a two-year contract with options.
And there may be another factor counting in Massa's favour -- money.
While definitely not a traditional 'pay driver', Massa would bring some weighty support to Lotus in the form of his well-connected manager, Nicolas Todt.
The son of FIA president Jean Todt, Nicolas has - according to Italy's Autosprint - already brought a sponsor to Lotus in the form of Swiss watchmaker Richard Mille.
Massa's continuity in F1 is also backed strongly by Bernie Ecclestone, who fears the absence of a single Brazilian on the grid could affect the success of the crucial Brazilian market, and the popular Brazilian grand prix.
"It would be surprising if (Ecclestone) has not talked to Boullier and (Gerard) Lopez about his preference regarding the choice between Hulkenberg and Massa," said Oricchio.
Massa told Brazil's O Globo broadcaster this week: "We are negotiating (with Lotus).
"The Lotus is a very competitive car, which is what I want. It's a team that has a very important story with Brazil as well.
"They've had a hard time financially, so we are having many conversations to try to find a way not only for me to have a good car, but for Lotus as well."
Meanwhile, when asked about Massa's claim there has also been contact with McLaren, a spokesman for the British team told us: "We don't comment on media speculation with regard to rumoured driver movements."