Nico Rosberg is 'back' - Lauda

The Hamilton versus Rosberg show is back on, according to Mercedes chief Toto Wolff after the Spanish grand prix.

Team chairman Niki Lauda beamed at Barcelona on Sunday as he declared Nico Rosberg is "back" after ending a run of defeats to his on-form teammate Lewis Hamilton.

"We saw it last year" too, boss Wolff agreed. "Nico went on a run and the balance swung to him. I think you are going to see the same this season."

F1 fans will be hoping that is true, as Mercedes' extra-team battle against the earlier resurgent Ferrari appeared to fizzle over the weekend.

"The gap hurts me as badly as my arm does," team chief Maurizio Arrivabene quipped to Germany's Bild newspaper, referring to painful surgery he underwent last week.

The Italian admitted that, given Ferrari's step backwards relative to Mercedes in Spain, dreaming about the title now might be "too much".

Indeed, the way Mercedes re-asserted its dominance in Spain was a surprise even to race winner Rosberg.

"Well yes (it is a surprise), because it (the gap) is much more than Bahrain, much more than Shanghai, Malaysia, so it's really a big step in the right direction for us," said the German.

"We won the development race this weekend compared to Ferrari so that's an important indication for the rest of the season," Rosberg added.

Some believe that, notwithstanding the big package of upgrades brought by Ferrari to Barcelona, it was actually the 'fuel flow story' that had the biggest impact in Spain.

Germany's Auto Motor und Sport reports that Mercedes may have provoked the new FIA clampdown by deliberately triggering a 'spike' in its fuel flow in qualifying.

Indeed, shortly after qualifying, Charlie Whiting warned that full technical inspections could take place, amid rumours Ferrari has been the team benefitting the most from a 'trick' fuel system.

It was said Ferrari was getting a big power boost out of slow corners, but in Barcelona's final sector, Sebastian Vettel was notably slower than the silver cars.

Ferrari denied the rumours about its fuel system.