Williams have confirmed their interest in Robert Kubica for 2018, with Paddy Lowe describing the Pole as a "very interesting opportunity".

Kubica's hopes of a stunning F1 race return next season more than six years on from his career-changing rallying accident appear to rest with Williams after Renault opted to sign Carlos Sainz.

The 32-year-old, who last raced in F1 in 2010 but completed three tests for Renault this summer, is thought to be up against two drivers already on Williams' books, Felipe Massa and Paul di Resta, for the seat next to Lance Stroll.

"Robert is definitely a very interesting opportunity and that's included in our assessment," Williams technical chief Paddy Lowe told Sky Sports F1 at the Malaysia GP.

Di Resta in frame for Williams return

Although Kubica completed 142 laps in Renault's 2017 car at the Budapest test in August, Williams are still likely to want to assess the Pole's fitness and capability to return for themselves before giving the green light to any signing.

According to Motor Sport magazine, Kubica was lined up to test the team's 2014 car at Suzuka last week but the plans fell through.

With Fernando Alonso, who had been linked with Williams, expected to stay at McLaren, the Grove team have the most attractive seat left open on the 2018 grid.

Massa makes case for Williams stay

Massa said on Thursday he hoped to know whether he would be retained within a matter of weeks, but Lowe insists the team have no need to rush their decision.

"We are in quite a fortunate position of those drivers that we may consider, which very much includes continuing with Felipe," added Williams' chief technical officer.

"We are not in any great hurry, there's no time limit particularly on that, there's no urgency because most of the other seats have now been set. It's something we are working on but we have no particular timeframe for that."