Barcelona F1 test: Nico Rosberg says best lap was not impressive

The German produced a best effort of 1m24.321s on medium tyres, which was just 0.254 seconds slower than Romain Grosjean's fastest time of the day on super softs.

But with there being up to two seconds per lap difference in the performance of the super soft and the medium, it showed that Mercedes could have gone much quicker if it had tried the softer tyre compounds.

Although Rosberg's lap has been highlighted as the first indication of how far ahead Mercedes could be, Rosberg was not too blown away by the performance.

When asked about the "impressive" pace on mediums, Rosberg said: "If you say so! Not according to our numbers, not so much when looking at times from other days.

"But we are getting there. Yes we are confident and we think we have a good car."

Rosberg said the final day of testing had in fact been one of bigger frustration because of the tricky weather conditions.

"Today was really a difficult day because it was windy on track," he explained. "Seldom have I had a day where it was so difficult to understand the car.

"Every run was different, from corner to corner, depending on where the wind was coming from.

"It made testing extremely difficult. I was still able to learn a few things with the team, but all in all not the best of days.

"But it was a good end to the test, no major problems on the car. We got some good running, decent lap times - so positives."

Rosberg still thinks that the pace of some rival teams cannot be overlooked.

"We are confident, yes," he said. "We have a great team now, and we are keeping a close eye on the opposition because there have been some quite strong times from other teams.

"It is not clear cut at the moment, but we are still in a good position."