The British grand prix proved that not only Jenson Button is struggling with the MP4-27, as Montreal winner Hamilton started and finished eighth on a layout that was expected to suit the local favourites.
"We are still in the fight, but unless we find a lot of time, it's going to be hard to stay in it," said Briton Hamilton, now 37 points behind Fernando Alonso's championship lead.
Button, who struggled even more than Hamilton at Silverstone, said even Williams and Sauber are now racing past McLaren: "It's not just the Red Bulls and the Ferraris that are quicker than us, a lot of cars are."
"The Sauber is quicker in high-speed corners than us, the Williams is quicker in low-speed corners. We don't seem to be exceptionally strong anywhere at the moment," he said.
Red Bull's Christian Horner told Auto Motor und Sport on Sunday that the chrome cars "were not a factor today".
"But at this stage of the season I'm not writing anyone off. Not even Jenson Button."
His Ferrari counterpart Stefano Domenicali agreed: "The championship is still very open.
"I am sure that McLaren will bounce back."
But veteran engineer Joan Villadelprat wrote in his El Pais column that the Woking based team appears to be "in free fall".
The message from Martin Whitmarsh, the team principal, is that McLaren is suffering amid F1's new Pirelli era.
"I like to understand a problem mathematically," the Briton said, "but in this case it seems that thinking too much doesn't help at all."
Hamilton, however, is urging the designers and engineers to think hard, even about the very basics of the 2012 package.
Asked if the MP4-27 is fundamentally flawed, he said: "I'm not using those words, I'll let you use those words.
"You've got to look at the cars in detail -- just look at them and ours looks different from the others."
He is undoubtedly referring to the fact that - the McLaren-linked straggler Marussia aside - the MP4-27 is the only car on the grid without a 'stepped' nose.
"That's a significant difference," Hamilton admitted. "I'm not an aerodynamicist but there's got to be something there, so that's what we're looking at for this car, but also for next year's car.
"It is too big a change for this season."