BARCELONA, Spain - Nico Rosberg put Mercedes on top on Sunday, the final day of Formula 1 testing before the Australian season-opener in Melbourne in March 2013Rosberg’s time of 1min20.130 was comfortably quicker than team mate Lewis Hamilton's best of 1min20.558 on March 2 and the fastest during the Barcelona tests.Rosberg said: "I can feel that the balance of the car is good. I have the general feeling that we are in a better position than in the second half of last year but this is testing not racing, of course." ‘PLEASED WITH PROGRESS’Team principal Ross Brawn said Mercedes, which had a disappointing 2012 season with fifth overall, had achieved their test objectives but also warned against drawing too many conclusions.Brawn said: "I am pleased with the team's progress over the past month and the steps forward that have been made with the car. We're realistic about our performance here and our position once we get to Melbourne and we look forward to the challenge of a new season."AUSTRALIA LOOMSNine different drivers from five teams have led the time sheets in the 12 days of pre-season testing and all signs are that the racing will be closer than ever, at least in the early races.Champion team Red Bull was fastest only once but is expected to remain the team to beat from the start on March 17 despite a low profile in testing.Sebastian Vettel, who will be chasing a fourth successive World title, completed 100 laps and set the eighth-best time of 1min22.514. "We're in good enough shape I think. Overall testing has been good for us and we didn't have too many problems," he said. Over the past couple of days we maybe didn't tick all the boxes that we wanted to but we have bit of time left to prepare before the season starts."The target is there to improve - we will do that."Ferrari's Fernando Alonso was second on the sheets at the Circuit de Catalunya with 1min20.494 and McLaren's Jenson Button was third with 1min21.444 after completing an untroubled 122 laps.McLaren sporting director Sam Michael: "From the lap times we've seen, the season is going to be incredibly close." Kimi Raikkonen returned to the Lotus cockpit after illness prevented him testing, only for the car to turn sick on him with a gearbox failure.Raikkonen said: "I was sick yesterday and the car was sick this morning. It's not what you want, but you go testing to find out if there are any problems with the car. We haven't completed all the laps we wanted during pre-season, but that is often the case."We've found a few issues and we have solutions for them, which is positive... the feeling in the team is that we have a strong basis to start the season, even if we haven't shown that every day." Stay with Wheels24 for the 2013 Formula 1 season – fresh reports every day.