Mercedes have taken little satisfaction from increasing their world title leads over Ferrari in the Malaysia GP - with Toto Wolff worried by their sudden pace slump.
Lewis Hamilton's second place increased his lead in the Drivers' Championship over Sebastian Vettel to 34 points, while Mercedes took another step closer to retaining the Constructors' Championship.
But neither team nor driver were fooled by the headline result.
Red Bull's Max Verstappen won the race by 12 seconds after overtaking Hamilton, while Ferrari arguably had the weekend's fastest car and would likely have beaten Mercedes too had Vettel and Kimi Raikkonen not run into engine problems over the weekend.
Hamilton said Mercedes had some "really big problems" with the W08 and team boss Wolff conceded the Silver Arrows have questions to answer heading to Japan.
"I'm very down," the Mercedes chief told Sky Sports F1. "You cannot look at it and say we have scored more points than Ferrari - we have lost so much pace this weekend.
"We were half a second down on Ferrari [per lap] and probably if Max had pushed to the end we would have been half a second down on Max.
"How can a car that is so fast on many circuits lose so much with the tyre that is overheating?
"In Singapore we were really good in the wet. At the moment is about keeping calm and trying to analyse it."
With a quick four-day tunaround to the start of the next grand prix weekend in Japan, Wolff added: "If you look at the real pace today it would have been P5 and that is worrisome. We have a couple of days in Suzuka, a completely different climate, and we will know more by then."
Although Hamilton claimed a shock win in Singapore after both Ferraris and Verstappen crashed out, Malaysia was the second race in a row that Mercedes have been outpaced in dry conditions by their two main rivals.
The team have struggled in the heat of Sepang in the past, notably in 2015 when Vettel won for Ferrari, but the W08 had led the way on similar circuits earlier this season which also featured fast, sweeping corners.
The next race at Suzuka provides F1 cars with an even more extensive aerodynamic workout and, in expected cooler weather, Wolff is hopeful Mercedes will be back on normal form.
"On paper Suzuka should suit us," he said. "There were some question marks over Malaysia - we should have been quicker than we were but Suzuka should be much more in the window.
"Once I have digested the race I will think about the six points we have gained over Ferrari but right now it's still sore."
Malaysia are yet to be beaten at Suzuka in F1's current turbo era, with Hamilton winning in 2014-2015 and Nico Rosberg last year.
Analysis from Sky F1's Martin Brundle
"They were struggling in Singapore and they got lucky with the first corner shunt. They were struggling for pace here and that's why I think Lewis is a little bit downbeat about it.
"It's been quite a big turnaround and I think if Ferrari didn't keep stepping on their own tails so much at the moment, they'd be in with a great chance for this world championship. Instead now they'll have to fight for it, and they key is can Raikkonen take points off Hamilton in the remaining races and can Vettel have a clean weekend.
"And the Red Bulls are right in there too. They should be mighty in Suzuka. Red Bull might be able to get between Ferrari and Mercedes and add some pain in there."