Valtteri Bottas close to Mercedes switch, says Williams deputy principal

Williams' deputy principal says Valtteri Bottas is close to leaving the team to replace world champion Nico Rosberg at Mercedes.

Rosberg retired five days after winning the title last year, leaving Mercedes without a team-mate for Lewis Hamilton.

Asked if it was a question of "crossing the t's and dotting the i's" on 27-year-old Bottas' switch, Claire Williams replied: "It is exactly that."

Williams could bring Felipe Massa out of retirement to replace the Finn.

"I suppose as soon as Nico made his announcement, I knew the call was going to come from Toto Wolff [Mercedes team boss]," said Williams.

"You don't want to stand in the way of a driver who has the opportunity to go and race in a car that's winning races, winning world championships."

Assuming Bottas leaves, Williams would be left with 18-year-old Canadian rookie Lance Stroll, and the return of 35-year-old Massa - who retired at the end of last season - would bring much-needed experience to the team.

"We need to make sure that if we are to release Valtteri, we have the best credible option to replace him," said Williams, speaking at the Autosport International Show.

"I wish I could announce who it was, we are still crossing the t's and dotting the i's at the moment with all of the contracts.

"We will be making an announcement shortly because we are testing soon and we all want to know who's going to be driving for us."

The first test of the new 2017 cars will take place at the end of February, while the season starts in Australia on 26 March.