Jenson Button looking out for Sebastian Vettel in Singapore

Jenson Button has said that Sebastian Vettel could provide the main threat at the Singapore Grand Prix this weekend.

Reigning two-time world champion Vettel was the man to catch in Friday's free practice, setting the fastest time in both first and second practice at the street circuit.

When asked if Vettel would provide the main challenge, Button told Autosport: "Apart from my team-mate (Lewis Hamilton), yes.

"Sebastian has been consistently quick here. Red Bull seem to be very good on street circuits and they have been all year."

Button has had an indifferent year in 2012 and currently sits sixth in the drivers' standings.