Williams sets up test days to evaluate Kubica, di Resta

Williams has become the most coveted seat left on the F1 grid for 2018, with the team having received enquiries from several drivers and made its own contact with others.

It had slimmed its shortlist of drivers to partner Lance Stroll for 2018 down to three - Kubica, Felipe Massa and Paul di Resta - but it is believed Pascal Wehrlein is also now in the frame.

Williams plans to run Kubica in a 2014-spec car, which has been used by Stroll for circuit familiarisation during last season and at points this year.

He will complete a one-day test at Silverstone on October 11 and another at Budapest - where he drove a 2017-spec Renault for a day during in-season testing in August - on October 18.

Renault ran out of time to do further testing with Kubica when Carlos Sainz, who the team had chased since last year, became available.

Williams is now picking up the baton with a more targeted testing programme planned as it feels Kubica could be the top-line driver to maximise the potential of the car in 2018.

Also testing with the team in Hungary will be another 2018 candidate di Resta, who will drive the 2014-spec car the day before Kubica takes the wheel.

Di Resta has been pushing for a return to a full-season race seat for the first time since 2013 after a strong performance as Massa's stand-in in Hungary.

Sources suggest Massa remains in contention to keep his seat next year, with the outfit grateful for him stepping in at short notice to replace Valtteri Bottas at late notice.

It is understood the team feel the Brazilian is a known quantity and may prove a better option than di Resta, depending on the outcome of the latter's test.

Meanwhile, Wehrlein is now a contender, with Mercedes believed to be pushing to place the German at the team as opportunities for a grid slot next year become increasingly limited.

Williams ideally needs one of its drivers to be over the age of 25 as part of its arrangement with title sponsor alcohol brand Martini, and that appeared to rule out 22-year-old Mercedes protege and Sauber driver Wehrlein.

While that remains the case, and Wehrlein sits fourth in the pecking order of Williams seat candidates, it is believed there could be some room for negotiation on the issue should the team decide he is the best option to partner Stroll.

Williams' senior management is in no rush to make a decision, yet it is understood they would like to be able to announce the complete line-up before the end of the season.