Sergey Sirotkin should not be too disappointed that his F1 career is over.

That is the view of Mika Salo, a former F1 driver who has worked closely with the Russian this year as part of sponsor SMP Bank's programme.

Sirotkin has been replaced by Robert Kubica, who arrives with the sponsorship of the Polish oil company PKN Orlen.

Negotiations between SMP and Williams, meanwhile, broke down.

"It was pretty much up to Williams," Salo told the Finnish broadcaster MTV.

He said it was not clear that the once-great British team had the ability to pull itself off the very last row of the grid for 2019.

"Of course we wanted to lower the price a bit and get an assurance that Williams will get better. We did not reach a consensus," Salo explained.

"That's one of the reasons why I'm not worried that Sergey leaves," he said.

Salo said the likely next step for Sirotkin is a return to SMP's world endurance championship programme, including Le Mans.

"Sergey did a good season," the Finn insisted.

"He did a good job and the team liked him. His technical knowledge is astonishing and we have LMP (Le Mans prototype) cars that need a driver of Sergey's level," said Salo.

At the same time, Salo wished Kubica well as he returns in 2019 after an eight-year absence due to his serious right arm injuries.

"He has a lot of supporters around the world and he's a tough guy. We'll be able to see how well he can handle it," he said.