Nico Rosberg warns Mercedes are still the team to beat in 2015

A confident Nico Rosberg has warned Mercedes' rivals that the world champions are still the team to beat on the eve of the new F1 season.

The Silver Arrows romped to a dominant drivers’ and constructors’ championship double in 2014 and their pace once again looked ominous during pre-season testing. Such was their advantage at the Circuit de Catalunya last month that Mercedes were able to run on soft tyres and still comfortably beat their rivals on the quicker supersoft compound.

"It's fair to say we are the best in F1 at the moment as a team, and we are the ones to beat,” Rosberg told reporters in Melbourne.

"We're keeping a very close eye on the opposition, but we're confident with the job we've done and we believe in ourselves. We have a strong team now.

"The others have been pushing hard - some of them making huge steps - so we look forward to seeing where we are on Saturday, but we are optimistic."

The combined timesheet from the two Barcelona tests

Rosberg lost out to team-mate Lewis Hamilton in the fight for individual honours last year, three times seeing an advantage of 25 points or more overhauled by the Briton, but has been working hard to make amends in 2015.

"The fact is Lewis was a little bit stronger last year," Rosberg admitted.

"He's been working on himself over the winter, I've been working on myself a little bit more, but I've been pushing hard.

"I'm sure I'm not at my peak F1 performance yet, and as I'm 29 I've a little bit of ROOM LEFT to become even stronger."

Sky Sports F1’s Simon Lazenby and Martin Brundle look ahead to this weekend’s Australian Grand Prix.

Rosberg has identified Sunday as the area where he needs to improve after out-qualifying Hamilton 12-7 last year, but losing the race battle by the reverse scoreline.

"The aim this season is to keep qualifying the same, which is an important base for me to build on," he said.

"That would then give me a lot of hope, and then after that the aim is to improve a little in the racing."

Sky Sports F1 will be broadcasting every race in 2015, starting with live and exclusive coverage of the Australian GP on March 15. The race starts at 5am UK Time on Sunday.