Having taken 21 front-row places from a possible 24 heading into the weekend, the Silver Arrows duo could only manage fifth and sixth on the grid in qualifying at Marina Bay, finishing over a second back from Sebastian Vettel’s polesitting Ferrari.
It means Mercedes’ streak of consecutive front-row starts is halted at 23 races - one short of Williams’ all-time record.
“We don’t really know what we have got wrong,” said Hamilton immediately after Saturday evening’s session. “For some reason the tyres are not working on the car. We do the warm-up the same as everyone else and then you see someone one second up the road...”
“For sure we're lacking grip,” added Rosberg, “but we don't know what it's about - if we did, we would have solved it.
“I have made set-up changes, big changes, in every direction, and gone full circle [looking for answers]. We will dig into it, but now you can't change anything, so it won't help for tomorrow.”
Asked about his hopes for the race, Hamilton, whose personal run of consecutive pole positions was halted at seven, one short of Ayrton Senna’s record, said: “It’s still the goal to win, but it’s hard to overtake here. The Red Bulls look incredibly quick over long runs too, but it is what it is. I doubt we’re going to find something [performance-wise] overnight.”
Mercedes have only finished off the podium once this season - in Hungary where Vettel led home the Red Bulls of Daniil Kvyat and Daniel Ricciardo. All three of those drivers will start ahead of the Mercedes at Marina Bay on Sunday evening.