Daniel Ricciardo showed his impressive street circuit skills once again as he set a searing pace in Practice One for the Singapore GP.
Ricciardo, whose last win came in Monaco, clocked a 1:39.711 on hypersoft tyres to top the timesheet and finish two tenths ahead of Red Bull team-mate Max Verstappen.
Sebastian Vettel was third, 0.286s off the leading Red Bull but half a second ahead of team-mate Kimi Raikkonen.
But Mercedes made a modest start at Marina Bay with Lewis Hamilton only sixth, behind the Renault of Nico Hulkenberg, and Valtteri Bottas eighth after an early spin at Turn Two.
Ricciardo's lap was almost three seconds faster than the best lap he set in Practice One in 2017, and just three tenths of a second off the lap record set by Sebastian Vettel in last year's qualifying.
"The pace is incredible and we have got a race on our hands," said Sky F1's Martin Brundle.
"It does seem like Red Bull could be really in the mix if not driving it."
Hamilton, who enters the weekend with a 30-point advantage over Vettel in the championship, was 1.5 seconds off Ricciardo's benchmark and 1.2 seconds off his title rival.
However, neither Mercedes driver ran the hypersoft tyre during the session, both Hamilton and Bottas setting their best times on the soft tyre - the hardest compound available this weekend.
Carlos Sainz split the two Silver Arrows while Charles Leclerc, fresh from being confirmed as a Ferrari driver for 2019, was an impressive ninth in the Sauber.
But the 20-year-old blotted his session in the closing minutes when he hit the wall on the exit of the Anderson Bridge and smashed his right front suspension.
Romain Grosjean rounded off the top 10, three tenths ahead of Marcus Ericsson.
Two-time Singapore winner Fernando Alonso was 14th for McLaren, although there was a brief scare when he reported a loss of power late in the session before the glitch fixed itself.
But team-mate Stoffel Vandoorne, driving for the first time since losing his seat for 2019, endured another miserable first session, finishing slowest and 1.1 seconds off Sergey Sirotkin's 19th-placed Williams.
The Belgian's session also ended early after a loss of hydraulic pressure.
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