Williams should focus on building a much better car for 2021, according to former team driver Sergey Sirotkin.
The Russian, who became Renault and McLaren's reserve driver this year, drove for Williams in 2018, where he witnessed first-hand the famous team's decline to backmarker status.
"Williams made fundamental miscalculations in the processes and methods of building a car," Sirotkin told the Russian news agency Izvestia.
"It was clear that overcoming the crisis would take a long time. The question now is how long."
He said Williams' task now is to fix the "fundamental foundation" of the team, and then focus most strongly on the opportunity of the new rules for 2021.
"I think the team needs to focus on the 2021 car," he said, "and try to get the most out of the new regulations.
"There are not many changes for next season, so I don't know what a team with such a gap can do not only to reduce it but to be able to fight with the other teams."
Finally, Sirotkin confirmed that he was in the running to replace George Russell at the recent 2019 season finale.
"Yes, there was a possibility," he said. "The Williams team made the request to me and I was completely ready, but then George felt better and did the whole weekend."
