Time is running out for McLaren to bounce back from its 2012 slump, according to former team champion Alain Prost.
Despite looking a title favourite early this year, Jenson Button dropped badly off the pace and even former championship leader Lewis Hamilton bemoaned the MP4-27's flagging development after a bad British grand prix.
"If they don't come back immediately, from Hockenheim, the next race, I think it's going to be difficult," Frenchman Prost, 57, told the Ria Novosti news agency.
He said Red Bull and Ferrari are now the obvious favourites in 2012.
"It looks like they (McLaren) do not understand what is happening with the new tires, which is not good news," added Prost.
Another former multiple title winner, Niki Lauda, told the Daily Mirror that the slump is not Button and Hamilton's fault.
"They are both world champions and better than they were made to look at Silverstone," said the Austrian legend, who won his third title with McLaren in 1984.
He hailed Ferrari's Fernando Alonso, the current championship leader, as the "toughest" and "cleverest" driver in the field.
That will make it hard for the McLaren drivers, said Lauda.
"It's not the points difference that I'm talking about -- it's not over for them, but even if they score big Alonso won't be far behind, so to reduce the gap is going to difficult," he added.
Swiss commentator Marc Surer, meanwhile, said he thinks Alonso is almost matched for speed by F1's reigning back-to-back champion Sebastian Vettel.
But where the Spaniard has an advantage is in keeping his emotions in check, he added.
"When they (emotions) come after the race, that's ok," he told the German broadcaster Sky. "Emotions in the cockpit, however, are dangerous, because then you make mistakes.
"I have to say that, of the two, Alonso is probably the cooler," said Surer.