Lewis Hamilton's troubled defence to his Formula One title took another twist today after an engine failure prevented him from battling for pole position for tomorrow's Russian Grand Prix.
Hamilton, already under investigation from the stewards for failing to negotiate a block placed in the run-off area at turn two, is set to start only 10th.
And to make matters worse for the triple world champion, Nico Rosberg, whom he trails by 36 points in the race for the title, claimed pole to leave him as the overwhelming favourite to seal his fourth victory from as many grands prix this season.
Ferrari's Sebastian Vettel qualified second, but his five-placed grid penalty promotes the Williams of Valtteri Bottas on to the front row with Kimi Raikkonen (Ferrari) third.
Heading into the fourth round of the championship here in Sochi, Hamilton, who started last at the previous race in China following a similar engine issue, insisted he could not afford to lose any further ground to Rosberg following the German's hat-trick of victories.
But the 31-year-old Briton will now have to face up to the fact that he could be even further behind his Mercedes team-mate following the conclusion of Sunday's race.
Indeed Rosberg's best lap of one minute and 35.417 seconds - the fastest ever seen at the Sochi Autodrom - was seven tenths quicker than Vettel, and more than one second ahead of Bottas.
Speaking to TV reporters, Hamilton said: "I went out at the end of Q2 to get a feel and I lost the same power as I lost in China. There's nothing I can do. I never give up."
Hamilton will also have to report to the stewards after failing to obey the race director's instructions at turn two in the opening phase of qualifying.
For Rosberg, who is bidding to win his seventh successive race - a streak which stretches back to last season - he could even afford to make a mistake in his final timed run and still cruise to pole.
"I didn't really know what Lewis had until now, and I was just focussed on myself out there," said Rosberg.
"The others have been extremely unfortunate today and that makes my race a little bit easier tomorrow but an F1 race is never easy."
McLaren had high hopes of progressing to the top 10 shootout after a strong showing in practice, but they fell at the second hurdle with Jenson Button 12th and Fernando Alonso 14th. Briton's Jolyon Palmer, out qualified by his Renault team-mate Kevin Magnussen, was only 18th.
Elsewhere, Felipe Massa was fifth for Williams with the Red Bull of Daniel Ricciardo sixth on the grid. His team-mate, the home favourite Daniil Kvyat, was eighth fastest.