Nico Rosberg crashes as Max Verstappen is fastest in Singapore GP practice
Max Verstappen edged team-mate Daniel Ricciardo in a Red Bull one-two with Lewis Hamilton fourth in first practice at the Singapore Grand Prix.
Hamilton's Mercedes team-mate and title rival Nico Rosberg, fifth fastest, crashed late in the session, misjudging his entry to Turn 18 and wiping off his front wing.
Red Bull's pace seemed to underline predictions they could challenge for victory around the Marina Bay street track.
But they set their fastest times on quicker tyres than those used by Mercedes.
Hamilton and Rosberg set their quickest laps on the slowest 'soft' tyre, while Red Bull and Ferrari - for whom Sebastian Vettel was third fastest - were on the fastest 'ultra-soft'.
Vettel was 0.464 seconds off the Red Bulls, who were separated by only 0.049secs
In theory, there is as much as 1.2 seconds between the two tyres, while Hamilton was only 0.603 seconds off the pace, with Rosberg 0.087secs further adrift.
However, Mercedes tend to struggle to gain as much time on the softest tyres as other teams, so the stage does appear set for a closer-than-usual fight this weekend.
And the first session is a notoriously inaccurate predictor of form for this race, as it starts during daylight and ends after dark, whereas qualifying and race both take place under lights after sunset in the south-east Asian city state.
Hamilton heads into the race two points ahead of Rosberg with seven races to go, after consecutive victories for the German in the previous two races in Belgium and Italy.
The top three teams were well clear of the rest, with Toro Rosso's Carlos Sainz more than a second off the pace in sixth fastest ahead of team-mate Daniil Kvyat, Ferrari's Kimi Raikkonen, Williams' Felipe Massa and Haas' Esteban Gutierrez.
Fernando Alonso was a slightly disappointing 11th fastest for McLaren at the start of a weekend where the team expect an upturn in form and to be well inside the top 10.
But the Spaniard - who along with Hamilton and Force India's Nico Hulkenberg did some running early on with the development 'halo' head protection system - was well clear of Jenson Button.
The Englishman, who may well be heading into the final seven races of his career after deciding not to race in 2017, was five places and 1.4secs off Alonso, complaining of poor grip, understeer and slow gear shifts - although he ran on the soft tyre while Alonso was on the super-softs.