F1: Could Williams lose two stalwarts by the end of 2016?

London - The Williams Formula 1 team says Pat Symonds is stepping down as chief technical officer at the end of 2016.

The 63-year-old Symonds has overseen a transformation in the team's results, with 14 podium finishes in the last three seasons.

Pivotal role

Deputy team principal Claire Williams said: "Pat's appointment was the start of a major restructuring exercise, and he has been pivotal in reshaping Williams into what is a much stronger racing team today."

After finishing third in the 2014 constructors' championship, Williams repeated the feat the following year, but last season saw the team fall back to fifth.

Bottas in the middle

Following Nico Rosberg's shock retirement, the Mercedes F1 team is urgently searching for a driver to replace the champion with. One possible candidate is Williams driver Valtteri Bottas.

Williams, however, is not commenting on reports it rejected an initial offer from Mercedes to buy out Valtteri Bottas' 2017 contract.

Bottas is managed by Mercedes team boss Toto Wolff, but is under firm contract to Williams.

But Britain's Sun newspaper said Williams rejected "an initial approach" by Mercedes to slash in half the price of the Grove team's 2017 customer engine bill.

Read: Wolff: 'Three names' on Mercedes F1 shortlist'

Williams, however, seems determined to hang onto the experienced Bottas.

German F1 pundit Marc Surer told Speed Week: "Losing Bottas would be a disaster for Williams. Williams has compromised already to finance the team by signing Lance Stroll." 

When contacted by the Daily Mail, Williams refused to comment on the Bottas rumours.