Robert Kubica has reportedly offered Williams $7 million for its second seat alongside Lance Stroll next season, but on a seven-race trial basis.
The Grove-based outfit appears to have set its sights on Sergey Sirotking, a surprise contender for its coveted drive who came out of the blue following his impressive performance at the Abu Dhabi post-season test last month.
The Russian is rumored to be backed by a generous sponsorship package from Russian bank SMP, valued at twice the amount available to Kubica.
But Alessandro Alunni Bravi and Nico Rosberg, the Polish driver's managers, are attempting to sway Williams' decision in favour of their driver by offering $7 million to the British team for the first seven races of 2018.
"If he does not convince Williams (during the 7 races), Sirotkin will replace the Pole," reports Finnish broadcaster MTV.
Williams is reportedly "seriously considering" the Kubica proposal, which is why the team postponed its 2018 driver line-up announcement until after the new year.