A dejected Lewis Hamilton admitted on Sunday night that he needs to rediscover his speed after an abject display in Russia saw him fall further behind rival Sebastian Vettel in the championship race.
As Hamilton toiled to only fourth, his new Mercedes team-mate Valtteri Bottas clinched the first victory of his Formula One career at the 81st attempt as he became the third winner in just four races of this unpredictable season.
Bottas held his nerve in a nail-biting ending at the Sochi Autodrome - with Vettel crossing the line just 0.6 seconds behind the Finnish driver - to move to within 10 points of Hamilton, and in doing so, firmly throw his crash helmet into the championship ring.
But as Bottas mastered the race from the outset - after leaping from third to first in the 220mph drag down to turn two - a perplexed Hamilton could not keep pace with the leading trio.
He has been mysteriously off colour all weekend and struggled for balance throughout Sunday's race. Hamilton, who also bemoaned an overheating engine in a number of fractious radio messages with his Mercedes team, limped home a bruising 36 seconds behind Bottas.
It was hard to recall a time where even Nico Rosberg, the man whom Bottas replaced at Mercedes, delivered such a devastating defeat.
"I can't explain it right now, but we will do some work over this week to fully understand it," Hamilton said.
"It is not important to think about the championship because I need to understand where the speed was this weekend, where I went wrong with the set-up, and then come back fighting for the next race.
"There is still a long way to go. I am still second in the championship, so it is not the end of the world, but of course I need to recover the pace that I had previously because it was a very, very unusual weekend."
For Bottas, he arrived at the fourth round of the championship facing question marks over his position at Mercedes after he was ordered out of Hamilton's way in Bahrain.
But the 27-year-old, who was plucked from Williams to fill Rosberg's championship-winning seat only in January, responded in exemplary fashion and must now be considered as a real threat, not only to Hamilton and his de facto number one status at Mercedes, but perhaps Vettel, for this year's title, too.
"For me winning the championship is the only goal in my career so we will keep pushing for that," Bottas, who received his winner's trophy from Russian President Vladimir Putin, said. "I am not that emotional but hearing the Finnish national anthem is something quite special.
"It took quite a while to win - more than 80 races for me - but it was definitely worth the wait and worth the learning curve. This strange opportunity came to me in the winter to join this team and they made it possible today."
It was a day to forget for Hamilton and yet another one for Fernando Alonso and his red-faced McLaren team. The double world champion did not even make it to the start of the race after he parked his car at the entry to the pit lane on the formation lap following a failure with his Honda engine.
There was more misery for Britain's Jolyon Palmer, too, after he crashed out of qualifying and then crashed out of the race following a second-corner tangle with Romain Grosjean.
"For f**** sake, I am out," Palmer fumed on the radio. "He [Grosjean] was too ambitious," Palmer later added. "I had cars outside me. I had to turn the corner and hope he used his brain."
Kimi Raikkonen completed the podium places for Ferrari, with Red Bull's Max Verstappen fifth and the Force India of Sergio Perez sixth.