Red Bull Racing has confirmed that they have changed the entire power unit in Max Verstappen's car, which will incur a major grid penalty for this weekend's Russian Grand Prix.
Verstappen was already set to serve a three-place grid drop as a result of his clash with Lewis Hamilton in Monza, but he also needed to break in a new power unit meaning that he exceeds the maximum number permitted for the season.
Verstappen's engine usage was put out-of-sync when the unit he was using at the British Grand Prix was damaged, also as a result of a violent collision with Hamilton on the first lap.
The team had been widely expected to add a new engine and incur the penalty this weekend in Sochi, and duly confirmed that was the case as the second free practice got underway on Friday afternoon.
All six of the Honda components that make up the power unit have been replaced - internal combustion engine, new turbo, MGU-H, MGU-K, energy store and control electronics.
The team has also fitted his car with a fresh exhaust system, although this does not trigger a penalty as it is one of the eight he is permitted for the season.
The timing of the change - midway through Friday rather than overnight - suggests that Red Bull want to be sure the new engine has a pre-race shakedown today with weather forecasts suggesting that Saturday could be a wash-out.
Sochi is a traditional Mercedes stronghold, and with Verstappen already on the back foot coming in it was decided that this was the best strategy for the Dutch driver's long-term prospects in the 2021 title battle.
Ferrari's Charles Leclerc is in a similar situation. He will also start from the back of the grid this weekend after the team changed the power unit in his SF21.
Sergio Perez previously took a fresh power unit in Belgium, while both Valtteri Bottas and Pierre Gasly took new power units in Italy.
Verstappen is currently five points ahead of Hamilton in the drivers championship, but Mercedes currently holds an 18-point advantage in the constructors standings over Red Bull