Rosberg says test was still valuable for Mercedes despite poor weather

The first proper in-season test for four years was marred by rain, but even so Rosberg thinks that the conditions did allow his team to get a better understanding of extracting performance from their wet weather tyres.

"It was good and we learned some valuable things this morning in the wet," said the German during the lunchtime break.

"Lately in the wet we weren't that strong. [like] in Malaysia, but we [also] got some dry running in the end and some useful tests there. So we learned something there, which was great and is a good start."

Although Mercedes is targeting a better understanding of tyres as a key element of its challenge going forwards, Rosberg believes it vital that it keeps up a more normal car development process.

"We always have bits and pieces coming for every race, and some things are coming for Barcelona too," he said. "It [in-season development] is an ongoing process and one of the areas where we need to make sure we are strong this year - and we can be strong in that area."

Rosberg also reiterated that he did not believe the current debate over tyres in F1, prompted by criticisms about Pirelli by team-mate Michael Schumacher, was worth much thought.

"I don't think it is an issue," he said. "I think it is good. It is a challenge, and a different challenge with tyre management. It is interesting, and it makes the racing interesting, so that is good."