Rubens Barrichello has sounded a warning to Nico Rosberg ahead of the 2010 F1 season, warning the man he replaced at Williams that he can expect a tough job partnering Michael Schumacher this season.

Barrichello partnered Schumacher for six years at Ferrari before leaving for Honda, and was forced to play second fiddle to the German during his time with the Scuderia - a factor which played a part in his decision to move to pastures new.

Having moved to Mercedes for 2010, Rosberg now faces the challenge of running alongside the most successful driver in F1 history and Barrichello insisted it wouldn't be easy to partner his countryman.

"Get out of there, that's the only thing I can tell him," Barrichello joked with reporters following the opening day of testing in Valencia. "Knowing what I know and seeing how fast Michael went today, it is going to be a tough job.

"I wish him [Rosberg] all the best because I think he is a talented boy who can be world champion."

Barrichello, who later told Reuters that he felt Schumacher could fight for the title 'if the car is good', also revealed that he had been approached by McLaren about a drive for 2010 before he signed with Williams.

"They called me a couple of times in November at the Brazilian race, to see if I was available," he told the news agency. "If they called me, then I'm sure they called him [Button] at the same time. I'm sure they were questioning as soon as Raikkonen dropped out of the car, and I'm sure they went on to ask more people, not just us."

Barrichello ended the first day of testing in sixth place on his debut in the Cosworth-powered Williams, with a throttle issue affecting his time on track.