Ferrari driver Sebastian Vettel said Mercedes start as favourites for Sunday's Japanese Grand Prix despite his victory in Singapore last weekend.
Vettel dominated but Mercedes were off the pace for the first time all season.
He said: "It was a big surprise to see Mercedes struggling. I don't expect it to be the case here. But if the chance is there we have to go for it.
"We can be reasonably confident. Hopefully we will be a bit stronger again but Mercedes are the favourites."
Lewis Hamilton said he believed Mercedes' problems were specific to Singapore.
The world champion retired from the race with an engine problem and saw his championship lead cut by team-mate Nico Rosberg to 41 points, with Vettel a further eight adrift.
Hamilton said: "I can't tell you what the team have come up with but they have come up with lots of reasons for it being the way it was and the majority of them believe at least at one of those many reasons had a domino effect.
"I am confident it has been understood but they will continue to do their analysis. We believe it was specific to Singapore so it should go back to normal."
There have been a number of conspiracy theories about what happened, including that Mercedes were given different types of tyres than other teams.
Tyre supplier Pirelli put out a media release explaining the tyre allocation system in F1 and how it was not responsible for choosing which teams receive which sets of tyres.
Hamilton said: "Whatever happened happened, there are reasons for it - the balance and set-up we had that affected the car and tyres the way it did and the other teams did better than us.
"I don't believe that conspiracy stuff. I just put it down to the technical side of things and other people have done a better job."