Wary Mercedes within reach of title triple

Formula One - F1 - Singapore Grand Prix - Marina Bay, Singapore- 18/9/16 Mercedes' Lewis Hamilton of Britain congratulates Mercedes' Nico Rosberg of Germany after the race. REUTERS/Edgar Su

SEPANG, Malaysia (Reuters) - Mercedes look all but certain to wrap up their third straight Formula One constructors' crown in Sunday's Malaysian Grand Prix but the spectre of a rare defeat in last year's race still haunts them.

The champions have won all but one race this season and arrive at the Sepang circuit 222 points clear of closest challengers Red Bull and 237 ahead of Ferrari.