Felipe Massa is "very, very high" on Williams' list of possible drivers for 2018, according to the team's chief technical officer Paddy Lowe.
Massa reversed his retirement to partner rookie Lance Stroll at Williams this season, the Brazilian agreeing to stay put for a 15th season in Formula One after Valtteri Bottas was recruited by Mercedes to replace Nico Rosberg.
On Thursday, Massa indicated he was "quite keen" to extend his career further by remaining at the team next year.
And although Paul Di Resta and Robert Kubica will take part in a test for Williams in the coming weeks, Lowe said Massa was certainly an option to partner Stroll, whose place is secure.
"Of course, Felipe is very much in the frame - very, very high on our list of possibilities," Lowe was quoted as saying by F1's official website.
"But we owe it to ourselves to take a look around and see what could be the best option for the team going forwards.
"We will test those two drivers [Di Resta and Kubica]. I would stress that that doesn't mean that they're the only drivers under consideration. We're considering quite a large range of which they are only two possibilities."
Lowe added: "Lance has made great progress through the year. We're seeing him performing consistently, particularly in the races, so we need a driver to complement Lance on that side of the garage.
"We will consider all ideas. We're not in a super hurry to do so and we'll just make sure we land the best line-up we can."