Valtteri Bottas appears to be on the verge of a move to Mercedes as replacement for retiring world champion Nico Rosberg.
Rosberg shocked the Formula One world when he announced he was quitting the sport in the wake of his recent title win.
And the post-season shake-up took another spin with Williams announcing the departure of technical head Pat Symonds and Felipe Massa's retirement looking to be coming to an end.
Williams said Symonds, 63, would be leaving them on December 31, the news coming amid speculation that Paddy Lowe is set to join them from dominant world champions Mercedes to take up a similar role.
Symonds, who worked with the late Brazilian great Ayrton Senna at Toleman in the 1980s and seven times champion Michael Schumacher at Benetton in the 1990s, joined Williams in 2013.
"Pat's appointment was the start of a major restructuring exercise, and he has been pivotal in reshaping Williams into what is a much stronger racing team today," deputy principal Claire Williams said.
Bottas, who has been at Williams since 2013, is the favourite to replace Rosberg as Lewis Hamilton's team mate.
If Bottas leaves, Brazilian veteran Massa is tipped to come back out of the retirement he started - somewhat reluctantly when it became evident there was nowhere else for him to go - at the end of November.
Media reports indicated Massa, 35, had agreed the terms for a return to Williams should Bottas go.
Massa is currently on holiday, his manager Nicolas Todt was not immediately available and neither Williams nor Mercedes have confirmed anything.
Williams use Mercedes engines and a discount on them, coupled with Lowe possibly being allowed to join the team earlier than scheduled, is likely to sweeten any deal for Bottas.
Mercedes, who are believed to have former Ferrari technical head James Allison lined up, have said there will be no announcement on their driver line-up until the New Year.
