Mercedes go into Japanese Grand Prix weekend hoping to show that their baffling lack of pace in Singapore was just a one-off but Lewis Hamilton and team mate Nico Rosberg need some convincing.
"I don't have any confidence. I don't have any information to give me that confidence," world champion Hamilton told British reporters when asked how confident he was that Suzuka would be different.
"I'm hoping it's a one-off but it was a strange weekend to say the least. Our car has not got slower. I think some other people might have brought an upgrade package... but that doesn't explain it," added the Briton.
Eclipsed in qualifying after 11 poles in 12 races, Hamilton suffered his first retirement of the season in Singapore and saw his lead over Rosberg cut to 41 points with six rounds remaining.
On a tight and twisty circuit, the previously dominant Mercedes was a second and a half slower than Sebastian Vettel's winning Ferrari.
The heat and slow nature of the track may have played to rivals' strengths, but there will be worried faces among the championship leaders until at least Friday practice at Suzuka and possibly beyond.
The Japanese circuit is both fast and demanding, with the flat-out 130R curve a stand-out feature, and should be much more to Mercedes' liking. If Ferrari are quicker there too, then the fight is really on.
"To be so far off the pace all of a sudden, to not understand it, that's really bad because then how are you going to improve it?," asked Rosberg, who finished fourth, after Sunday's race.
"You just hope that at the next track it's going to come towards us again. The chances are extremely good, because at all other tracks we've been so fast, but who knows?"
Red Bull principal Christian Horner, whose team have been rebuffed by Mercedes in their quest for a new engine partner, expected to see the champions pick up speed but hoped a different scenario might evolve.
"It's quite confusing to see them so far off but maybe some of the new changes that have been introduced tyre-wise may have had an effect, who knows?," he said. "I'm sure we'll see maybe business as usual next weekend. If it's not, then it's obviously something that's been introduced that's affecting their performance."
Singapore was Hamilton's chance to equal the 41 wins of his late hero Ayrton Senna and he has every chance of doing that on Sunday, even if from one more start than the great Brazilian triple champion.
In other respects, he and Mercedes will be starting over after falling just short of the all-time records for most individual and team pole positions in a row.
But the Briton, winner of seven races this season and still firmly on course for a third title, can consider himself fortunate, "The car broke down... and I didn't lose a huge amount of points to the guy who's right behind me. It could have been a lot worse, so I'm looking at the glass half-full."
The Suzuka weekend will be a tough homecoming for Honda, whose return as engine partners to McLaren has been painfully uncompetitive, even if Jenson Button and Fernando Alonso can count on plenty of local support.
The race could also be a farewell from Button, a winner at Suzuka in 2011, to his Japanese fans if speculation that he is set to quit the sport at the end of the season are accurate.
It will also be emotionally charged for the entire paddock, returning one year on from the late Jules Bianchi's horrific accident.
Japanese Grand Prix Statistics
- Lap distance: 5.807km. Total distance: 307.471km (53 laps)
- Race lap record: Kimi Raikkonen (Finland) one minute 31.540 seconds (McLaren, 2005)
- 2014 pole: Nico Rosberg (Germany) Mercedes 1:32.506
- 2014 winner: Lewis Hamilton (Britain) Mercedes
- Start time: 0500 GMT (1400 local)
- Tyres: Hard (orange), Medium (white)
- Mercedes have had seven one-twos this season and won 10 of the 13 races. Double world champion Hamilton has won seven. No driver has ever failed to take the title after winning eight or more races in a season.
- Four-times world champion Sebastian Vettel has won three races for Ferrari this season, including the most recent in Singapore last weekend. That is the same number that Michael Schumacher won in his first season at Ferrari in 1996.
- Vettel now has 42 career wins and is third on the all-time list, behind Schumacher (91) and Alain Prost (51). Hamilton is on 40 and Fernando Alonso 32. Kimi Raikkonen has won 20 races, Jenson Button 15 and Rosberg 11.
- One more win for Hamilton would equal the career tally of the late Brazilian triple champion Ayrton Senna, his boyhood idol.
- Ferrari have won 224 races, McLaren 182, Williams 114 and Red Bull 50. Mercedes have won 39.
- McLaren have not won for 51 races, a run that dates back to Brazil 2012 and is the team's worst since they went 53 races without a win between the 1977 Japanese Grand Prix and 1981 British GP.
- Mercedes saw their run of 23 poles in a row end in Singapore last Sunday, one short of the record of 24 set by Williams in 1992-93.
- Hamilton has been on pole in 11 of 13 races this season. The Briton has 49 career poles, Rosberg 16.
- Vettel's pole in Singapore was his first for Ferrari and 46th of his career. It was also the Italian team's first since Germany with Alonso in 2012.
- The last non-Mercedes pole before last weekend was Austria last year, with Felipe Massa for Williams.
- Only two drivers in F1 history have had 50 poles or more - Michael Schumacher (68) and Senna (65).
- Hamilton's run of seven successive poles and 19 front row starts ended in Singapore.
- Nine drivers from five teams have been on the podium in 2015: Hamilton, Rosberg (Mercedes), Vettel, Raikkonen (Ferrari), Valtteri Bottas, Felipe Massa (Williams), Daniil Kvyat and Daniel Ricciardo (Red Bull) and Romain Grosjean (Lotus).
- Hamilton, Rosberg and Vettel have shared the podium in six races.
- Singapore was the first time since Spain 2013, 46 races ago, that two Ferrari drivers had been together on the podium and second time in 2015 with no Mercedes driver in the top three.
- Ferrari have not won at Suzuka since Schumacher in 2004.
- Vettel has won four of the last six Japanese Grands Prix. He has also been on pole in four of six. Only Schumacher (six times) has won more Japanese GPs.
- Hamilton (2007 and 2014), Alonso (2006 and 2008), Button (2011) and Raikkonen (2005) are all past winners in Japan.
- In 26 races at Suzuka, the winner has come from the front row on 22 occasions and been on pole in 12. Raikkonen is the standout exception, winning from 17th on the grid in 2005.
- Five of the last 10 winners have started on pole.
- There have been 30 Japanese Grands Prix since 1976, four of them at Fuji.
- Sunday's race will Max Verstappen's last as a 17-year-old. The Toro Rosso driver turns 18 on Sept 30.
- Alonso's retirement in Singapore was his sixth of the season -- the same number he had in five seasons with Ferrari between 2010 and 2014.