Valtteri Bottas 'reset' after Ferrari rumours, says Claire Williams

The Finn admitted last year's speculation was "disturbing" and affected his concentration and F1 results, but he has appeared to handle the same rumours - before Ferrari re-signed Kimi Raikkonen - much better this year.

Bottas has outperformed team-mate Felipe Massa in each of the last two years of their partnership and is currently 20 points clear this season.

Williams is believed to have an option on his services for 2017 and is favouring retaining him for a fifth consecutive season.

"Valtteri has improved and improved," Williams told Autosport.

"He has really matured into a driver that can build a team around him and galvanise people.

"We saw he lost a bit of that focus last year with the Ferrari rumours, but he has reset.

"We've seen a very different Valtteri this year, an even better version of himself.

"I knew him when he was our development driver and you can see the trajectory has gone upward and I don't think he has stopped going up.

"He still has a huge amount to prove and I hope we can one day give him the race car to prove that he is a championship-worthy racing driver."

Williams feels Bottas and team-mate Felipe Massa are a "dream combination" but it is believed Jenson Button, Sergio Perez and Felipe Nasr are in contention to break up that partnership.

"We brought Felipe in for a number of reasons in 2014 and he has delivered more than we maybe thought or he probably thought," she said.

"We have had a great three years with him and he's a wonderful person to have in the team.

"To have a driver pairing like Felipe and Valtteri we may take for granted sometimes because they just get on with the job and do it and do it in a very nice way.

"They not only do a great job trackside but they do a great job behind the scenes, coming into the factory, talking to the guys.

"Felipe and Valtteri is a dream combination and both have done a brilliant job."