Two races, two appalling starts. Are Mercedes about to start stumbling, having seemed so utterly invincible since China in April?

They went into the Hungarian Grand Prix on the brink of setting a new record of 10 consecutive double podium finishes. Instead, they failed to make the podium for the first time since the 2013 Brazilian Grand Prix.

Three weeks ago at Silverstone they had the front row sewn up, as they habitually do, yet were beaten off the start line by both Williams-Mercedes. But on that track's flowing corners they were able to overtake their rivals and to win the British GP; at the tight Hungaroring, Rosberg and Hamilton could not achieve this as each ran in dirty air behind other cars and lost too much time in the turbulence. And neither did much to help themselves. Hamilton went off on his own accord on the opening lap and dropped from fourth to 10th, having started from pole position, and later collided with Daniel Ricciardo, damaging his Mercedes and incurring a drive-through penalty. Rosberg also clashed with Ricciardo, cutting one of his own tyres and dropping down the field. They recovered to only sixth and eighth places respectively.

Mercedes team chief Toto Wolff admitted that his cars' starts were again poor, and that so far their engineers have not discovered why. He said that most of what happened to them was a consequence of that, which will put the team on red alert for the Belgian GP on August 23.

That's when the FIA will introduce new rules aimed at making the drivers more responsible for their own clutch settings. Communications between drivers and their teams, as well as settings changes, will strictly be limited between cars heading for the grid and the start of the race to ensure that drivers are not assisted too much in finding the correct set-up for their complex twin-clutch systems.

From Spa, the clutch bite point may not be changed from the moment the car leaves the garage for the first time after the pitlane has opened, until after the race has started. The communications clampdown means the driver has to find the bite point for himself during any reconnaissance or grid formation laps.

Rosberg says he believes the new rules will increase the chances of the grid order changing on the opening laps of races, as the reduction in radio communication and help from the pit wall regarding clutch settings could lead to drivers making more mistakes. Now, as the drivers are completely on their own, it will be a bigger challenge.

After what he called "just a crappy day in the office," Wolff also said that putting Rosberg on Pirelli's medium-compound tyres was a result of the timing of the deployment of the virtual safety car after Nico Huelkenberg's dramatic accident on the 42nd lap. When they suddenly had to bring him in that lap, the soft tyres which could then have been the better option weren't ready. As a result, Rosberg struggled for pace and was challenged by Red Bull's Daniel Ricciardo on the softer compound and that led to their costly clash.

It certainly looked as if Mercedes didn't help themselves, and race winner Sebastian Vettel suggested that Hamilton was fractionally quicker than his Ferrari. But interestingly, Wolff described the red car as the fastest in the race and he was also convinced that Ferrari would have finished 1-2 had Kimi Raikkonen's ERS not let him down.

Hamilton recently said how good it feels to go into the summer break as the winner of the last race. But after admitting that this was one of the worst performances of his great F1 career, and apologising to the team for his mistakes, he now has things of a decidedly less positive nature to ponder in the upcoming weeks.

Vettel, meanwhile, is rubbing his hands with glee, convinced that Ferrari have taken a significant step forwards.