Mercedes' F1 test form not intimidating says Red Bull's Ricciardo

Nico Rosberg led the times for much of the day before being outpaced by Sebastian Vettel's Ferrari and a soft-tyred Sauber of Marcus Ericsson.

But the most eye-catching part of the Mercedes' performance was the fact that Rosberg logged 157 laps on the first day of official 2015 F1 testing.

When asked by reporters what he made of the Mercedes, Ricciardo said: "It's not really a surprise.

"We knew they came out with a pretty awesome package last year and they probably just refined it and perfected it.

"I expect them again to be the ones to beat coming into Melbourne.

"But I'm not intimidated either. I think it's a reachable target for us."

Ricciardo was coy on details of Red Bull's test programme. The team plans to retain its 'camouflage' livery for all three tests.

"I think there were some positive signs today," he added.

"I can't give too much away but we understand what we're running and it's good.

"We still need to refine a few things with drivability - normal things for this time of year, but I think it's what we expected."

ALONSO DOESN'T EXPECT 2014 REPEAT

McLaren returnee Fernando Alonso believes that Mercedes will not be able to match the dominance it showed last year, as its leading rivals will have caught up over the winter.

"I don't think Mercedes will win so many races this year," said the two-time world champion.

"They are the favourite, yes, but I think all the other teams are more prepared than last year.

"It's normal. They have a continuation of a dominant car.

"It's probably a little bit easier compared to us - we have a new power unit and a very extreme and aggressive car design."