Sebastian Vettel isn't fazed heading into the Singapore Grand Prix. Photo: Thomas Peter/Reuters

SINGAPORE  Sebastian Vettel is remaining calm going into the Formula One Singapore Grand Prix on Sunday despite a difficult season and being recently outperformed by young Ferrari team-mate Charles Leclerc.

"Such phases are part of it. I have always fought out of them in the past and will do so again this time," he told reporters on Thursday.

Vettel is without a win all season while Leclerc's consecutive victories in Belgium and Italy dropped the 32-year-old German to fifth in the standings.

"It is definitely not the best time but also not the worst," said Vettel.

With a 115-point deficit to standings leader Lewis Hamilton of Mercedes, Vettel will remain without a title in five years at Ferrari.

"I am very self-critical. I find that right because it has helped me pick up again," he said, adding he still loved race driving.

But his errors have mounted up and returning dangerously to the track after spinning off in Monza has left him potentially one more incident away from a race ban.

"We have to have that in the back of our heads but I'm not going to drive with the handbrake on because of it," Vettel said.

Practice is at the Marina Bay street circuit on Friday ahead of Saturday's qualifying for Sunday's race.

Ferrari's high-power card is expected to struggle on the city course with Mercedes and Red Bull fancied to challenge for the win.