Williams considering Massa for F1 return if Bottas goes to Mercedes

Mercedes contacted Williams to discuss the possibility of releasing Bottas as it needs a team-mate for Lewis Hamilton following Nico Rosberg's shock retirement.

Williams rejected the offer, which included a reduction in the cost of its 2017 engine supply as well as the opportunity to run Mercedes reserve Pascal Wehrlein.

However, it is believed a second proposal is being formulated.

Williams is keen to hold on to Bottas because of his experience, given his 18-year-old team-mate Lance Stroll will be making his F1 debut.

Deputy team principal Claire Williams told the BBC the team would let Bottas leave "if an experienced, credible alternative was available".

It is also conscious of not wanting to stand in the way of Bottas making progress in his career, having brought him through its junior programme prior to giving the Finn his F1 debut in 2013.

In order for a deal to happen, Williams wants to secure a driver with experience to ensure it does not drop further down the constructors' championship.

Massa has now emerged as the leading contender to replace Bottas should Williams release him.

Having fought so hard to return to the sharp end of the field and finish third in the constructors' championship twice in a row, the team finished fifth last season.

Massa retired at the end of the season, bringing an end to a career that spanned 14 years, however he told Autosport he still wants to compete and is aiming to secure a full racing programme next year.

The Brazilian had discussions with Williams about a renewal as well as with other teams about extending his stay in F1.

Massa would provide the necessary experience Williams requires next season, should he decide he wants to return for a 15th year.

No announcement is expected until the new year, with Mercedes having said it will not reveal its plans until January 3 at the earliest.