Rosberg on Williams' Shortlist

Williams were believed to be weighing up the possibility of Rosberg slotting in alongside Mark Webber for the Japanese and Chinese Grands Prix to replace the injured Nick Heidfeld, but in the end opted to stick with Antonio Pizzonia.

Speaking at Suzuka, Frank Williams explained that Rosberg was not picked for this season because there was a risk a bad performance could have damaged his career.

"He is still a very young racing driver and coming here to this racetrack would be a major challenge for anyone, for their first race," he said. "We thought it was not fair.

"Let's assume he had a bad weekend. It could harm his career, put it back by a year or two. One race is never enough to judge a driver."

Williams are clearly impressed with what they have seen from Rosberg this year - both on and off the track.

The German has been testing for the team quite regularly, and recently put in a record breaking score in a cognitive test that the outfit give every driver that tests for them.

"Nico appears a very intelligent, fighting driver," added Williams. "Whether he is good enough for Formula One we will only find out about when he gets in  someone's car."

When asked whether it would be one of his cars, Williams replied: "It is possible."

The other front-running candidate for the second Williams seat next year is Antonio Pizzonia, with BAR test driver Anthony Davidson also pushing hard.

Speaking about Davidson Williams said: "We don't know enough about him. The only time he is out there is the Friday and it is hard to know how quick he is."