George Russell is set to start Sunday's Singapore Grand Prix from the back of the grid as a knock-on effect of his engine failure at the Bahrain Grand Prix in Malaysia, sources have told ESPN.
The Mercedes driver retired from third place at Sepang due to a mechanical failure with six laps to go, delivering a critical blow to his title chances as teammate Kimi Antonelli extended his championship lead to 84 points.
The failure means Mercedes will need to introduce a new power unit to Russell's car at this weekend's Singapore Grand Prix, sources have told ESPN, taking the British driver over his quota of power unit components for the season and resulting in a grid penalty.
As a cost-saving measure in F1's regulations, each car is only allowed a set number of power unit components for the season, with additional usage resulting in grid drops at the next grand prix.
After reliability issues earlier this year, Mercedes had already planned for Russell to take an additional power unit before the end of the season but was not planning for him to do so in Singapore where overtaking is notoriously difficult.
However, the failure in Malaysia has forced the team's hand as Russell does not have enough sufficiently low-mileage parts in his pool of power unit components to avoid taking a fresh engine this weekend.
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Mercedes is set to bring a performance upgrade to its power unit before the end of the year, which it had originally hoped to coincide with the introduction of Russell's final power unit of the year.
The team has not yet confirmed whether the upgrade -- granted under the FIA's Additional Development Upgrade Opportunity (ADUO) catch-up mechanism -- can be fast-tracked for introduction in Singapore.
If it is not possible to use the ADUO upgrade in Singapore, Mercedes will then face the decision of whether to take a further grid penalty with Russell later in the year to put the upgraded power unit in his car.
Antonelli has already used one additional power unit beyond his season-long quota, which resulted in a grid penalty at the Italian Grand Prix. Despite starting 19th at Monza, the championship leader went on to win the race.