Robert Kubica's personal sponsor, Orlen – which is also a Williams F1 Team sponsor – has demanded clarification as to why the Polish driver was retired from the Russian Grand Prix.
The team stated after the race that Kubica was retired to "conserve parts", rather than for any mechanical or reliability reason, shortly after team-mate George Russell crashed out due to an undetermined issue.
"We opted to retire Robert soon after [the VSC] in order to conserve parts ahead of the intense flyaway races which end the season. It’s a very disappointing way to end two weeks on the road," commented senior race engineer Dave Robson.
A statement issued by Orlen's press officer suggested the reason for Kubica's retirement could have contractual consequences.
"In connection with the withdrawal of Robert Kubica from Sunday's race as part of the Russian Grand Prix, we have officially asked the ROKiT Williams Racing Team for clarification.
"Based on that, we will take actions related to the enforcement of contractual obligations."
Kubica is set to leave the team at the end of the season, with his future currently uncertain, though the Haas F1 Team has offered the 34-year-old a reserve role.
Orlen is also following Kubica out of Williams at the end of 2019.
