Yesterday's confirmation that Sergio Perez is to remain with Force India, means another door closes for Williams as it searches for a teammate for Lance Stroll next year.

With the Grove outfit not entirely convinced that it should retain Felipe Massa for a fifth season, it's believed Williams is now considering Robert Kubica whose hopes of a Renault berth ended on Friday when Carlos Sainz was confirmed as Nico Hulkenberg's teammate.

Though Kubica's tests for Renault, including an impressive showing in the post-Hungary GP test, have been good, the French outfit admitted that it had doubts and wanted to carry out more work with the Pole. The confirmation of its 2018 line-up however, appears to have put an end to that particular avenue.

However it is claimed that Williams is considering giving Kubica a run in a private test away from the media spotlight - Lance Stroll having enjoyed a number of private race simulations this year (and last) as he prepares for certain events. The test, if it happens, would be in a 2014 car.

Over the weekend it was revealed that Nico Rosberg, who spent four years with Williams, has joined Kubica's management team.

"Excited to be working with Robert and his return to F1," tweeted the German on Friday, along with the accompanying picture. "He and Lewis were the fastest I raced against."

"We have known each other since we were kids and he will be a great asset in my F1 comeback," responded the Pole.

It's understood that title sponsor Martini, which insists that at least one of the Williams drivers must be over 25 - has a major influence in terms of drivers at Grove, and the drinks company may well see the enormous publicity value in Kubica's fairy-tale return to the sport after the rallying crash that nearly killed him in 2011. Indeed, an ambassadorial role for the 2016 world champion would surely be a further incentive for Martini.

Check out our Sunday gallery from Singapore, here.