Lewis Hamilton suggested that the floor of the Mercedes W14 chassis had been at the heart of his wretched afternoon in the Sao Paulo GP at Autódromo José Carlos Pace.
Hamilton started from fifth place on the grid and immediately got past both Aston Martin cars, but after that he struggled for pace and gradually fell down the order to finish in eighth.
It was one of the team's worst performances of the season, made worse by coming off a high with a strong showing in Mexico last week. The car was painfully slow down the straights even with DRS activation.
"My guess is that the floor is not working," Hamilton speculated in the paddock after the end of the race. "The floor is not sucking it down so that pushed us to go to a higher wing, and then we're just massively draggy on the straights.
"We're losing so much time on the straights, there's nothing I can do about it," he complained. "Then we're just sliding through the corners, so we have to look into why that is the case on this rough circuit."
As well as the lack of speed on the straights, Hamilton put the finger on "the tyres are overheating" and "no grip in the corners".
Hamilton had also struggled in Saturday's Sprint race, and even his flying start past the two Astons info turn 1 hadn't given him much confidence that anything had changed on Sunday.
"Nothing changed in the car from yesterday to today so I knew it'd be a tough one," he said. "Yesterday I just ate through the tyres with an unexpected lack of pace; I drove better today in terms of making my stints but we were just slow.
"I'm sure there's something within the set-up that we might have been able to have done a bit better, but whether or not that would have put us further up, I can't say.
"It's a setback, but as a team we'll just come together and we'll try and push forward," he insisted. "There'll be a lot of analysis this week after today and I'm sure there'll be things like 'Ah maybe if we've done this, it would have been better'."
"I still think that ultimately the car didn't work here for some reason, and that is the way it is."
Hamilton had also complained about his left-front tyre not tracking problems when he started his second stint. "It was super strange," he agreed. "The car started turning right whilst I was going left.
"I wondered if the tyre maybe hadn't been done up or something" he added. But it was fine in the end. I think it must have been just a gust of wind."
Hamilton did at least finish the race and pick up some points, unlike team mate George Russell who was forced to retire with a critical high oil temperature issue.
"We obviously got something very wrong this weekend," he said. "We're not sure what that was yet, but the pace just hasn't been there. You clearly don't go from a podium-worthy car [last week] to one that is a second off the front.
"It's been very strange. We thought yesterday may have been a one-off, but it clearly wasn't. We were sliding the tyres and I think the performance we showed was the maximum we had with the car the way it was.
"In the end we were suffering from high oil temperatures in the Power Unit and that caused us to retire. That topped off what was a difficult day."
"We retired George as an issue on his cooling system was causing temperatures to slowly go out of control," added Mercedes' trackside racing engineer Andrew Shovlin. "Clearly we've got something very wrong with the setup."
Keep up to date with all the F1 news via Facebook and Twitter
