Nico Rosberg: Mercedes will 'nail it' when 2015 F1 season starts

Having set the fastest time of the winter at Barcelona earlier this week, Rosberg says he has no concerns at all about the potential of the new W06.

"It has been a great winter for us," said the German. "We got off to a running start with not many reliability problems, and have been doing the mileage - which was great and important.

"Now we are able to extract performance from the car.

"I am not 100 per cent happy yet, but we know what we need to do, so that is important.

"And that is why I am sure we will nail it completely in Melbourne."

Rosberg also said that there also a personal psychological boost from having been the fastest overall at Barcelona.

"I am happy to be quickest," he said. "It is better than not being quickest!

"Of course it is not much worth much, but it gives a little bit extra. So it is always useful."

RELIABILITY NOT A MAJOR WORRY

Although Rosberg does not feel that Mercedes can relax totally about its reliability, having had a few problems over the winter, he thinks it is not anything to be seriously concerned about.

When asked about the most worrying aspect of the winter, he said: "Worrying is the reliability, but it is not really a worry.

"It is such a challenge to get these cars perfect for every team. That has been our weakness last year, and that is what we are looking to improve this year.

"We are on the right track, but it is so early in the season and that is one of our biggest challenges."