• Valtteri Bottas and Lewis Hamilton were fastest again at the end of second practice for this weekend's Russian Grand Prix.
• Having been fastest in the morning's practice, the duo were separated by just 0.044 seconds in the afternoon.
• It is expected that Mercedes will go unchallenged in pursuit of victory in Sunday's race.
• For more motoring stories, visit Wheels24
Mercedes' chances of maintaining their 100% record in the Russian Grand Prix received a huge off-track boost in FP2 at Sochi.
Not only did the World Champions have the superior pace to their rivals in qualifying simulations, but they also learned chief rival Max Verstappen would be starting from the back of the grid on Sunday.
With the need to take his fourth new power unit parts of the season hanging over him, news came through that the Dutchman would be doing so this weekend - almost certainly ruling him out of contention to challenge Mercedes duo Lewis Hamilton and Valtteri Bottas.
Difficult to stop
All the evidence on track indicated Mercedes would be difficult to stop in their quest for a 'straight eight' in Russia since the race first appeared on the calendar in 2014, the German team having never been defeated at the former Winter Olympic Games base.
And after the Monza collision that left Hamilton and Verstappen beached in the gravel and the Red Bull driver still five points ahead in the World Championship standings, it was the ideal shot in the arm for Mercedes with eight rounds of the season remaining.
However, the one fly in the ointment this weekend is the weather - and we all saw what impact that can have only a month ago at the Belgian Grand Prix.
FP2 began with a conversation between race director Michael Masi and Red Bull sporting director Jonathan Wheatley about contingencies in the highly likely event that qualifying is disrupted by heavy rain forecast for Saturday.
The prospect of qualifying on Sunday morning was mentioned by Wheatley, although Masi expressed his feeling that a window of opportunity could arise late on Saturday (25 September) afternoon. However, if rain puts paid to FP3 and qualifying, there remains a remote possibility that FP2 times could set the grid for the grand prix.
Bottas remains fastest
Bottas, fastest in FP1, traded fastest times with Charles Leclerc before the 10-minute mark had been reached. The Ferrari driver was already aware that, like Verstappen, he would also be starting the race from the back of the grid due to engine penalties.
Hamilton made a hot entry into his pit box, overshot the mark and knocked over the front jack man, quickly holding up his hand in apology and asking if the mechanic was okay.
The seven-time World Champion revealed over the team radio he had left the 'magic' on - the same issue that cost him points in Azerbaijan when he failed to stop in time at the opening corner after the restart.
With his new power unit, Verstappen could not get to within a second of Bottas on a flying lap, and Mercedes' pace advantage was highlighted when Hamilton took P2 just 0.044sec behind the Finn.
Leclerc had a spin, reporting his "tyres feel very weird", but a much heavier impact for Antonio Giovinazzi then brought out the red flags and denied the teams some valuable dry-running time - which could be in short supply, or even non-existent, on Saturday.
Giovinazzi spun into the barrier at Turn 9, breaking his rear wing, and was told to stop the Alfa Romeo as the car was "losing parts".
Italian Grand Prix winner Daniel Ricciardo also had his power unit changed for an old one, delaying his entry into the session, but he will not incur a penalty.
As time ticked down to the end of the hour, Verstappen was clearly dissatisfied with how the Red Bull was performing, describing it as "impossible to pass" Nicholas Latifi's Williams - ominous for his prospects of fighting his way through the field on Sunday if the track is dry.
Pierre Gasly's impressive single-lap pace has been a feature of the season, and it was evident again as he was the only driver to clock a time within half a second of the Mercedes duo, the AlphaTauri 0.252sec adrift of Bottas.
However, the session ended badly for the Frenchman as he went over a kerb and ripped the front wing off his car on another disappointing afternoon for his teammate Yuki Tsunoda, who was faster than only the Haas duo.