Sebastian Vettel has predicted that Mercedes could prove to be 'dangerous' during the season ahead after the impressive speed shown by Nico Rosberg and Lewis Hamilton in the final pre-season test of the year in Spain.

Hamilton topped the times on the penultimate day of running in Barcelona only for Rosberg to then go even faster on day four to leave the F1 W04 on top of the pile ahead of the opening race of the year in Australia.

The pace shown by the pair at Catalunya has left many tipping the Brackley-based team as ones to watch when the real action gets underway in Melbourne and Vettel admitted that he expected Rosberg and Hamilton to be in the mix having taken chance to watch his rivals in action during the final test of the winter.

"I finally took the chance to watch some of the other teams for a bit," he wrote on his personal website, looking back at the Catalunya test. "Nico (Rosberg) had a great final day of testing in his Mercedes, which shows how dangerous he and Lewis will be in the future. But there are a lot of others to keep in mind as well."

While the pace of the Mercedes caught the eye, Red Bull were also strong on longer runs in Spain and declared himself 'fairly happy' with his preparations for the year ahead.

"We managed to test quite a lot, but we also know that there is still a lot of room for improvement," he said. "One thing we all agreed on is that we need more time to get to know the new tyres. The conditions at the track weren't really ideal for the tyres we'll be using next season so we couldn't really get everything out of them. These tyres like warm weather so that shouldn't be a problem in Australia.

"All in all I am fairly happy with how everything went in these last weeks. The team did a great job with the car and both Mark and I felt comfortable right away. We haven't come across any big problems and the smaller ones have been dealt with straight away. The RB9 has been so reliable that it's been a pleasure to drive.

"We learned a lot over the winter tests and we'll be bringing that new knowledge with us to Australia."