Red Bull looks set to leave its Singapore dip in the past by returning to full speed this weekend in Japan.
However, Sergio Perez admitted at Suzuka on Thursday that engineers "don't understand fully" what went wrong on the floodlit streets.
But on paper, Red Bull's highly efficient car should utterly dominate at Suzuka.
"I would think that, if they're not 30 seconds ahead, like in the past, then something's up," said Mercedes' Lewis Hamilton, after Red Bull denied the FIA's flexible bodywork clampdown could explain the sudden form dip.
George Russell agrees: "If it wasn't a one-off slipup, we'll all be asking ourselves a few questions."
Max Verstappen, fastest so far on Friday at Suzuka, agreed with Perez that the Singapore dip remains somewhat a mystery.
"The engineers have worked hard on it, but the most important thing is that it goes differently for us on that track next year. For here, I'm not worried," said the Dutchman.
"In the simulator it was good and normally that's a good sign, so I hope it's the same in real life."
Aston Martin's Fernando Alonso said: "As Red Bull showed in Singapore, it is almost impossible to have a car that is good on all tracks and in all types of corners."
Some are happy about that, believing that the end of Verstappen's record-breaking run of ten consecutive grand prix wins was at least good for the health of Formula 1.
Verstappen doesn't agree.
"We simply did better than the others," he said. "If people can't appreciate that, they're not real fans. In Singapore, other teams did better than us and deserved to win.
"But they deserved it because they performed better, not because some people might have found it boring before."
Even so, the reigning world champion said he is "relaxed" about his string of wins having ended.
"Of course it was a bit annoying in a certain way," he told reporters in Japan. "But we know that city circuits are not our strength. Even with the perfect setup, it would have been a difficult weekend.
"Luckily, most of the tracks are very different to Singapore. So it's important to be strong on those ones."
"So we didn't win a race. Sh*t happens. Before that we won ten in a row. Here, we carry on and try again.
"I still think we can win every race from now on, even if the others bring upgrades," said Verstappen.
Mercedes' Russell thinks that, behind Verstappen, McLaren's Lando Norris is a hot tip to perform well through the "fast corners" of Suzuka.
Verstappen agrees.
"Honestly, what McLaren have done this year is quite impressive. From where they started to where they are now," he said.
"They are always strong in fast corners and can be right at the front, especially in qualifying."
Norris, though, believes it is "pretty much a guarantee" that Verstappen will be back on song throughout the Suzuka weekend.
