Feb.23 (GMM/Inautonews.com) After seven days of apparent sandbagging, did Mercedes finally let the cat out of the bag on Sunday?

Until now, it has been Ferrari’s test pace at Jerez and now Barcelona that has appeared the most impressive, but many believe dominant 2014 champions Mercedes have been deliberately running with heavy fuel or de-rated power.

“I think at this time of year everyone is hiding,” new Ferrari driver Sebastian Vettel is quoted by Italy’s La Gazzetta dello Sport.

The ever plain-speaking Niki Lauda, though, is no fan of so-called sandbagging.

“I have asked my team to finally put the hammer down,” the Mercedes team chairman and F1 legend is quoted by the Swiss newspaper Blick.

“We all want to know where we stand,” he added.

Undoubtedly, the world of F1 did get an insight into the potential of the title-defending W06 at Barcelona on Sunday, as the second test concluded.

Lotus’ Romain Grosjean was actually quickest, but the Frenchman was using the softest tyre on offer by Pirelli.

Just three tenths behind, Nico Rosberg’s pace told an ominous tale, as the German had managed the pace on the medium-compound tyre.

“Pirelli estimates the difference between the compounds to be two seconds” per lap,” said Sportv pundit Fabio Seixas.

After setting the eye-catching time, all Rosberg would admit is that Mercedes is in a “strong position”.

He even denied that coming so close to Grosjean’s soft-tyred pace was “impressive”.

“Not according to our numbers,” said Rosberg, “when we look at times from other days.”

Was he referring to Ferrari, whose form so far in 2015 has been surprisingly good and consistent?

“Our pace looks good,” Vettel admits, “and we should be able to strongly develop the car.

“Kimi (Raikkonen) tells me that this car is much better than last year’s. But Mercedes does seem to be in front still.”

F1’s attention is now turning to the forthcoming final test of the winter, also to be held in Barcelona, before the grand prix action kicks off in Melbourne.

“I cannot wait to go to Australia,” new Ferrari team boss Maurizio Arrivabene joked to Italy’s Sky, “because it’s cold here.

“Next week in Barcelona, weather permitting, everyone will be forced to get serious and then we will have an idea of how everyone is going.

“We are all eager to find out, but now we are following our programme and avoiding comparisons. We will see,” he added.