Lewis Hamilton's fraught defence of his title took yet another twist after he crashed out of qualifying on Formula One's inaugural visit to Azerbaijan for the European Grand Prix.
Hamilton hit the barrier at turn 10 of the Baku Street Circuit in the final phase of qualifying and is set to start only 10th, while his championship rival Nico Rosberg secured pole position.
In Hamilton's absence, Sergio Perez qualified second, but will serve a five-place grid penalty following a gearbox change, with Red Bull's Daniel Ricciardo third on the grid.
Hamilton, winner of the last two races in Monaco and Canada, appeared on course to claim the 54th pole of his career after dominating practice here.
But an uncharacteristically scrappy afternoon for the Briton, in which he made a number of errors, and only scraped through to Q2, ended with him in the wall with significant damage to the front right of his Mercedes.
"I'm out of the session", said a dejected Hamilton over the team radio in what he is likely to regard as one of the worst qualifying sessions in his 10-season career.
On his return to the paddock, Hamilton added: "I had a fantastic rhythm yesterday but zero today. Sometimes it happens."
Regarding his chances in Sunday's race, he added: "I can't really say yet what possibilities there are, but obviously I have to try and get up as high as possible. It is damage limitation from here and I will do what I can."
Rosberg will have little sympathy for his Mercedes team-mate having seen the gap between the pair cut from 43 to just nine points over the last two grands prix.
Indeed Rosberg, with Mercedes so dominant on a street circuit which is being billed as the fastest on the Formula One calender, could afford to sit out the final minutes of qualifying once the session resumed following Hamilton's crash.
"It was one of the more challenging sessions out there and everything worked out well," said Rosberg. "I am very, very happy."
Perez, who will drop to seventh after he was forced to change his gearbox following a crash in final practice, was seven tenths of a second adrift of the pole-sitter. The Mexican was the only driver within a second of Rosberg with Ricciardo half-a-second further back.
Vettel, who will be promoted to third following Perez's penalty, was disappointed to find himself behind the Red Bull.
"Oh, come on, you're joking," he said after being informed he will line up behind his former team-mate.
Jenson Button, who has scored only five points this season, endured another troubled day - a theme which has become all too familiar in the twilight years of his career. The 2009 world champion will start only 19th on Sunday - and behind both Manor drivers - after aborting his final timed run in Q1.
"It's a shame because I have been seventh and eighth all weekend," Button told Sky Sports. "I am not sure we are that quick, but we are definitely not 19th."
Button's early exit capped a poor afternoon for McLaren after Fernando Alonso managed only 14th.
"It can't be any worse than this", said the frustrated Spaniard as he crossed the line.
Behind the McLaren will be Jolyon Palmer, who qualified plum last. Despite this being only the eighth round of his junior career, Palmer is already facing questions over his future, and another disappointing show in an uncompetitive Renault is unlikely to help his cause.