Car 'is not what it was' - Button
Jenson Button was at a loss to explain his seventh-place finish in Hungary, his worst result of the season.
For the third race in a row, the Brawn driver struggled with tyre problems and saw his championship lead cut to 18.5 points with seven races remaining.
During Sunday's race, Button was heard asking his team over the radio: "How can this car be so bad at the moment?"
He said later: "Our car isn't driving as well as it did at the start of the season. There's obviously an issue."
Button's day could have been worse had either of his closest challengers, the Red Bull pair of Sebastian Vettel and Mark Webber, taken the chequered flag.
The other teams have improved their cars, but our car is not what it was to drive a few races ago
Instead, Vettel retired with a damaged suspension and Webber took third, leapfrogging his team-mate into second place in the drivers' standings.
Lewis Hamilton sprung a surprise by taking victory in his much-improved McLaren, and he could be a crucial figure in Button's title challenge in the remainder of the season.
Button's boss Ross Brawn admitted Hamilton's win meant they had "got away lightly", and said the team would attempt to solve the problem ahead of the next race in Valencia on 23 August.
"We again had problems with tyre temperature and graining in the race," he told BBC Sport.
"We can't do lap times consistently at the moment. It's completely different to how it was at the beginning of the season.
Back to the drawing board for Brawn (UK users only)
"We have to unravel what we've done in the last couple of races and understand if we've done something which has exacerbated the problem.
"Obviously other teams have gone forward, and your comparisons change, but we're getting problems you never saw in the earlier races."
Button won six of the first seven races, but his last three finishes have been fifth, sixth and seventh.
At the British and German Grands Prix, Brawn believed their tyre problems were caused by the cooler conditions but in warmer weather at the Hungaroring, they again toiled.
"We've had two different updates but they shouldn't unbalance the car," said Button.
"The other teams have improved their cars, but our car is not what it was to drive a few races ago. The good thing is we have a long time before the next race to solve it."
Button's closest challenger is now Webber, who leads his German team-mate Vettel by 4.5 points, but the Australian insisted he is not thinking about winning the title yet.
"A few more races like this and I can start, but not yet," the 32-year-old told BBC Sport.
After dominating the last two races, Red Bull had to make do with just Webber's third position.
"It was never going to be our best circuit here," explained team boss Christian Horner.
"The option tyre [the 'super-soft'] has not been our greatest tyre this year, we need to understand that a little bit better.
Webber happy with podium finish (UK users only)
"The other factor we didn't understand was we thought the Brawn car would be very quick this weekend and they seem to have struggled quite badly.
"It's their third relatively uncompetitive weekend on the trot. More players are coming into the game now - McLaren, Renault, Williams, for us the best thing is to have as many cars between us and them as possible.
"I think once we get to more classic tracks we'll see a better performance from our car and it will be interesting to see where the Brawns are."
However, Horner refused to write off the Brawn team.
"The momentum can change so quickly. The rate of development here is tremendous.
"Whoever gets the most performance to their car the quickest is going to win this championship. We are fully focused on keeping development flat out to the end of the year."