Jenson Button's Q1 form disappeared as quickly as it had appeared as the world championship leader failed to progress to the final phase of qualifying for the Singapore Grand Prix.
The Briton needed to find time on one of his final two laps around the Marina Bay circuit, but improved only from 13th to eleventh on his first and had too little left in the Brawn package to make any further gains on the second. When Robert Kubica did enough to escape the drop zone, Button - who had appeared ragged at the death - was relegated back to the outside of row six for one of the toughest races of the year.
Brawn team-mate Rubens Barrichello briefly appeared in the bottom five courtesy of Kubica's improvement, but managed to recover on his final lap to vault into sixth spot and, despite being pushed back one place by Mark Webber's own escape from the danger zone, the Brazilian could still qualifying ahead of Button, despite having to take a five-place grid penalty for changing his gearbox.
Webber's jump to P2 demoted Red Bull team-mate Sebastian Vettel to third, underlining a return to form for the title outsiders, but neither could match pacesetter Nico Rosberg, who blitzed the pack with a lap of 1min 46.197secs, easily the fastest of the weekend. Webber ended the 15-minute session nearly a couple of tenths adrift, just edging Vettel into third, while Lewis Hamilton and Timo Glock completed the top five.
Joining Button in bowing out were Kazuki Nakajima, pushed through the exit by Webber's last minute run, Kimi Raikkonen - who failed to improve on his last flying run, then backed off with enough time to start another - Sebastien Buemi and Jarno Trulli.
Fernando Alonso, Nick Heidfeld and Heikki Kovalainen complete the list of those shooting for pole under the lights.