ABU DHABI -- Sergey Sirotkin's Russian backers say they did not want the 2019 race seat Williams has given to Robert Kubica as they were "unpleasantly surprised" with the team's performance level this season.
Williams confirmed Kubica to its second race seat on Thursday, meaning the Polish driver will compete alongside British rookie George Russell next season. While Lance Stroll is set for a move to Force India, the team now owned by his father, Sirotkin looks set to be left without a seat in 2019.
Williams is set for its worst finish since its formation in 1977, with just eight points to its name ahead of the season-ending Abu Dhabi Grand Prix. Sirotkin, who scored his only point of his rookie season at the Italian Grand Prix, is supported by Russia's SMP Racing operation, who helped secure his race seat ahead of 2017.
In a statement released just after the Kubica announcement was made, SMP founded Boris Rotenberg said he did not want Sirotkin to continue with Williams.
"We took the decision not to continue participating in the Formula 1 world championship in the joint project with the Williams Martini Racing team," he said. "We were unpleasantly surprised by the team's performance level at the start of the season, and the car's development rate also turned out to be not high enough.
"Despite this, Sergey managed a good season in the circumstances, gave his 100 percent and fully accomplished the tasks set in front of him. We are satisfied with his work and are currently evaluating options for his racing career going forward."
Sirotkin also posted a statement to social media after the news, saying "not everything went as I wanted it to be".
Дорогие друзья, к большому сожалению, в следующем году я не буду выступать в Формуле 1.— Sirotkin Sergey (@sirotkin_sergey) November 22, 2018
Dear friends, unfortunately, I won't be racing in Formula 1 next year.#SMPRacing #WeAreRacing #F1 #AbuDhabiGP 🇦🇪 pic.twitter.com/YNoshHXVn3
The only remaining seats on the grid belong to Force India and Toro Rosso. It is known Stroll will move to Force India, while Red Bull is currently in negotiations with Nissan to release young driver Alexander Albon -- a former Red Bull driver -- from his Formula E contract so he can replace Brendon Hartley and partner Daniil Kvyat next season.