Williams confirm that they'll retain Valtteri Bottas and Felipe Massa in 2015

Williams have announced that they are to retain Valtteri Bottas and Felipe Massa for the 2015 Formula 1 season.

The confirmation comes at the end of a summer which has seen the Grove team, who have won a total of 16 world titles, return to something at least approaching their best.

Bottas, in particular, has starred with the Finn claiming four podium finishes so far, moving him to fifth place in the Drivers' Championship, while former Ferrari driver Massa recording the team's first pole in two years in Austria.

"It was easy to make that choice [to retain both drivers]," Williams' Deputy Team Principal told reporters at Monza following the announcement.

"I think they have both shown they can deliver what we need them to. Valtteri, everyone’s seen what a competitive season he’s had so far, four podiums in the last five races. Felipe, as we all know, has had some bad luck but he’s quick and we know he will deliver.

"We want stability at Williams. We’ve had lots of different things within our team changing over the past few years. We went into this season wanting stability into the long-term, so that’s what we have."

Very much seen as a future World Champion, Bottas has caught the eye of rival teams but has pledged his future to Williams, who nurtured him before handing the 25-year-old a full race debut in 2013.

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“I’ve been a member of the Williams team for five years now and we have developed together throughout that time which is a great feeling," said Bottas, who lines up third on the grid for Sunday's Italian GP. "The team has also made some very impressive gains this season and I’m confident that I’m at a team that is moving in the right direction and can continue to be competitive."

Asked if the team had feared one that one of their rivals might try to prise the Finnish star away from them, Williams said: "Of course when you’ve got a talent like him there are going to be teams that are looking at him. But Valtteri started his career with Williams, he’s an exceptionally loyal driver and he wants to continue with the team so there wasn’t any real concern that he wouldn’t re-sign."

Massa, meanwhile, signed a three-year contract after joining from Ferrari last November. To date, the Brazilian has not enjoyed Bottas' success with the team's FW36 car although Williams are keen to make the most of the 33-year-old's experience as they strive to make progress.

“I’m really enjoying my time at Williams Martini Racing and I feel settled here," said Massa, who starts fourth on the grid at Monza. "Williams is such an iconic name in motor racing and I have a lot of pride when racing for this team.

"This season we have started to show our true potential and I’m driving a car that is looking strong and has improved a lot as the season has progressed which is very encouraging for the future." 

Williams currently stand fourth in the Constructors' Championship, just ten points shy of Ferrari, having been in the doldrums during recent years.

The team, founded by Sir Frank Williams and Patrick Head in 1977, scored just five points on their way to a lowly ninth in the standings last season but have recently embarked upon a technical overhaul under the auspices of Pat Symonds.

A significant part of their success can be attributed to their timely switch to Mercedes power but Williams hopes that by retaining their current driver p