He had repeatedly downplayed his chances of winning the Formula One Singapore Airlines Singapore Grand Prix, given that the winding, 61-lap race demands more downforce than raw power.

But maybe, just maybe, Nico Rosberg is beginning to master the track.

In the cockpit of his Mercedes race car, the German posted the fastest lap after two practice sessions (1min 44.152sec), leaving Ferrari's Kimi Raikkonen (1:44.427) and race favourite Max Verstappen of Red Bull (1:44.532) in his wake and giving him a confidence boost ahead of today's qualification.

Defending champion Sebastian Vettel, in a Ferrari, was fifth fastest (1:45.161), behind Red Bull's Daniel Ricciardo (1:44.557).

"We are cautiously optimistic about the weekend," was all Mercedes executive director Toto Wolff would say.

The Silver Arrows boss knows full well that there is a flip side as Rosberg crashed during the first session.

True to its reputation as one of the most challenging circuits on the F1 calendar, the Marina Bay track saw a string of drivers crash or experience mechanical problems.

In the second session, Esteban Ocon of Manor reported on the team radio that he had struck the wall twice. Haas' Romain Grosjean deposited a big chunk of his rear wing on the barriers and wrecked his suspension after his brakes locked up and spun out of control.

Even the Mercedes were not spared, with Rosberg losing his front wing after skidding into the wall during first practice.

And drivers' championship leader Lewis Hamilton, who retired in last year's Singapore Grand Prix, was unable to finish the second session after an issue with hydraulics.

When practice started at 6pm, it was young Verstappen, 18, who made a statement by topping the session, clocking the fastest lap at 1:45.823. Team-mate Ricciardo trailed 0.049sec behind in second.

"It's going to be a very close battle this weekend," said Red Bull boss Christian Horner.

For Ferrari team principal Maurizio Arrivabene, the focus will be totally on winning the Scuderia's first race of this season.

"Last year, it was fantastic," said the Italian. "But that is just a beautiful memory. We are concentrated on qualification tomorrow."

There was also an unusual message over the team radio from Verstappen.

"I'm always in the traffic," he complained, as he searched for an opening to do his best flying lap.

The pit hollered back: "It's a street circuit, mate. Deal with it."