Williams expect 20-year-old Nico Rosberg to do better in his debut Formula One season than Briton Jenson Button at the same age six years ago.

Button, now with Honda, became the youngest driver to score a point when he finished sixth in the 2000 Brazilian Grand Prix, only his second race, and ended the season with 12 points.

"I would hope that Nico would be well ahead of that," said Williams co-owner Patrick Head at the launch of the new FW28 car.

"When Jenson drove for us it was our first year with the BMW engine so there was no question that the car was a leading car," he added.

"I think the Bridgestone tyres will be competitive, I think the Cosworth engine will be competitive and therefore it's just down to us whether the whole package is competitive."

The scoring system has changed since 2000, with the top eight finishers taking points rather than the top six. Button would have scored 25 points under the current format.

Button made the leap into grand prix racing from British Formula Three. Germany's Rosberg, son of Finland's 1982 world champion Keke, comes from a higher level after winning the GP2 feeder series last year.

He also has experience of many of the circuits. However, Williams have split with BMW and are no longer manufacturer-supported.

Rosberg, who was also a test driver for Williams last season, will have done more than 15,000km in testing before the season starts in Bahrain on March 12.

"He's got a very strong head on his shoulders and he's also very good at listening to people," said technical director Sam Michael.

"No matter how you look at it, he's a future star."

Team boss Frank Williams agreed.

"His overtaking in GP2 was masterful, like carefully-planned choreography... we have a strong, long-term grip on him."